Basic Economic Concepts

Scarcity

Scarcity is the fundamental economic problem: human wants are unlimited, but the resources available to satisfy those wants are limited. Because resources are finite and wants are infinite, not all wants can be satisfied. This forces society to make choices about how to allocate its scarce resources.

Scarcity exists for all goods that have a positive opportunity cost. If something is scarce, it has a price greater than zero.

Resources (Factors of Production)

Factor	Description	Reward
Land	All natural resources (e.g., soil, minerals, water, forests)	Rent
Labour	Physical and mental effort contributed by people	Wages
Capital	Man-made goods used to produce other goods (e.g., machinery, tools, factories)	Interest
Entrepreneurship	The ability to organise the other factors of production and take risks	Profit

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Choice and Opportunity Cost

Because resources are scarce, society must choose which goods and services to produce and which to forgo. Every choice involves a trade-off.

Opportunity Cost

Opportunity cost is the value of the next best alternative forgone when a choice is made.

Key points:

• It is the NEXT BEST alternative, not all alternatives combined
• It includes both explicit costs (money paid) and implicit costs (the value of what you gave up)
• Opportunity cost is subjective -- it depends on the decision-maker's preferences

Examples

Example 1: A student has 3 free hours. She can either study for an exam (next best alternative) or go to a movie. If she chooses the movie, the opportunity cost is the exam preparation she could have done during those 3 hours.

Example 2: A farmer has a piece of land. He can grow either rice (expected revenue: HKD 50,000) or wheat (expected revenue: HKD 40,000). If he chooses to grow rice, the opportunity cost is HKD 40,000 (the wheat revenue forgone).

Example 3: A government can spend HKD 10 billion on building a hospital or on building a school. If it chooses the hospital, the opportunity cost is the school that could have been built.

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The Economic Problem

The economic problem arises from the combination of scarcity and unlimited wants. It forces every society to answer three fundamental questions:

1. What to produce? Which goods and services should be produced, and in what quantities?
2. How to produce? How should resources be allocated to produce these goods? What production methods should be used?
3. For whom to produce? How should the output be distributed among the population?

Different economic systems answer these questions in different ways.

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Free Goods vs Economic Goods

Feature	Free Goods	Economic Goods
Scarcity	Not scarce (abundant)	Scarce (limited relative to demand)
Price	Zero (free)	Greater than zero
Opportunity cost	Zero (no alternative forgone)	Positive (alternative forgone)
Examples	Air (in most places), sunlight, rain water	Food, clothing, cars, houses

A good can be free in one context and economic in another. For example, clean air is a free good in a rural area but may become an economic good in a polluted city (people pay for air purifiers).

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Production Possibility Curve (PPC)

Definition

The Production Possibility Curve (also called the Production Possibility Frontier, PPF) shows the maximum combinations of two goods or services that an economy can produce, given its current resources and technology, when all resources are fully and efficiently employed.

Assumptions

1. The economy produces only two goods
2. Resources are fixed in quantity
3. Technology is constant
4. All resources are fully and efficiently employed

Shape of the PPC

The PPC is typically concave (bowed outward from the origin). This reflects the law of increasing opportunity cost: as more of one good is produced, increasingly larger amounts of the other good must be sacrificed. This occurs because resources are not equally efficient in producing both goods (resources are specialised).

If resources are equally efficient in producing both goods, the PPC is a straight line (constant opportunity cost).

Key Points on the PPC

Point on/relative to PPC	Interpretation
On the curve	Resources are fully and efficiently employed
Inside the curve	Resources are underutilised (unemployment, inefficiency)
Outside the curve	Unattainable with current resources and technology

Shifts of the PPC

The PPC can shift over time:

Outward shift (economic growth):

• Increase in the quantity or quality of resources (more labour, better education, more capital)
• Technological improvement
• Discovery of new resources
• Allows the economy to produce more of both goods

Inward shift:

• Decrease in resources (war, natural disaster, population decline)
• Allows the economy to produce less of both goods

Movement Along the PPC

A movement along the PPC represents a reallocation of resources from producing one good to producing the other. This shows the opportunity cost of producing more of one good.

Worked Example

An economy can produce the following combinations of good X and good Y:

Combination	Good X (units)	Good Y (units)
A	0	100
B	1	95
C	2	85
D	3	70
E	4	50
F	5	0

The opportunity cost of producing the 3rd unit of X is:

Moving from C to D: Good X increases by 1 unit, Good Y decreases from 85 to 70 units.

Opportunity cost = 15 units of Y.

The opportunity cost is INCREASING:

• 1st unit of X: 5 units of Y (100 to 95)
• 2nd unit of X: 10 units of Y (95 to 85)
• 3rd unit of X: 15 units of Y (85 to 70)
• 4th unit of X: 20 units of Y (70 to 50)
• 5th unit of X: 50 units of Y (50 to 0)

Worked Example: PPC with Constant Opportunity Cost

An economy can produce either 300 computers or 600 mobile phones, using all resources. Assume constant opportunity cost.

The PPC is a straight line from (0, 600) to (300, 0).

Opportunity cost of 1 computer = 600/300 = 2 mobile phones. Opportunity cost of 1 mobile phone = 300/600 = 0.5 computers.

Equation: M = 600 - 2C (where M = mobile phones, C = computers).

If the economy produces 100 computers: M = 600 - 200 = 400 mobile phones. This point is on the PPC (resources fully employed).

If the economy produces 100 computers and 300 mobile phones: this is inside the PPC (M = 400 is the maximum), indicating underutilisation of resources.

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Economic Efficiency

Productive Efficiency

An economy is productively efficient when it is operating on its PPC -- it is producing at a point where it is not possible to produce more of one good without producing less of another. This requires that all resources are fully employed and used in the most efficient way.

In the context of a single firm, productive efficiency means producing at the lowest possible average cost (at the minimum point of the average cost curve).

$\mathrm{Productive efficiency: } \mathrm{MC} = \mathrm{AC}_{\min}$

Allocative Efficiency

An economy is allocatively efficient when it is producing the combination of goods and services that best satisfies society's wants. This occurs where the marginal benefit (MB) of the last unit produced equals its marginal cost (MC).

$\mathrm{Allocative efficiency: } P = \mathrm{MC}$

When $P \gt MC$, society values the good more than it costs to produce -- more should be produced. When $P \lt MC$, the good costs more to produce than society values it -- less should be produced.

Pareto Efficiency

A situation is Pareto efficient if it is impossible to make any one person better off without making at least one other person worse off. A Pareto improvement is a change that makes at least one person better off without making anyone worse off.

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Specialisation and Division of Labour

Specialisation

Specialisation occurs when individuals, firms, or countries concentrate on producing a narrow range of goods or services in which they have a comparative advantage.

Division of Labour

Division of labour is the breaking down of the production process into separate tasks, with each worker (or machine) specialising in one or a few tasks.

Advantages of division of labour:

1. Increased productivity: Workers become more skilled at their specific task through repetition
2. Time saving: No time is lost switching between tasks
3. Training efficiency: Workers can be trained more quickly for a single task
4. Use of machinery: Tasks can be more easily mechanised when they are simple and repetitive
5. Higher output: Overall production increases, lowering average cost

Disadvantages of division of labour:

1. Monotony and boredom: Repetitive tasks can reduce worker motivation and job satisfaction
2. Interdependence: If one stage of production breaks down, the entire process stops
3. Lack of versatility: Workers may only know one task and cannot easily switch jobs
4. Alienation: Workers may feel disconnected from the final product (Marxist critique)

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The Three Fundamental Economic Questions

1. What to Produce?

This question asks which goods and services should be produced and in what quantities. The answer depends on:

• Consumer preferences and demand
• Available resources
• Government priorities

In a market economy, consumer demand (through price signals) determines what is produced. In a command economy, the government decides.

2. How to Produce?

This question asks about the methods of production -- labour-intensive vs capital-intensive techniques.

• Labour-intensive: Using more workers and fewer machines (common in developing countries where labour is cheap)
• Capital-intensive: Using more machines and fewer workers (common in developed countries)

The choice depends on:

• Relative costs of labour and capital
• Available technology
• Quality requirements

3. For Whom to Produce?

This question asks how the output of the economy is distributed among its population.

• In a market economy, distribution depends on income (which depends on ownership of factors of production)
• In a command economy, the government determines distribution based on its priorities (e.g., equal distribution, based on need)

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Positive vs Normative Economics

Positive Economics

Positive economics deals with objective, testable statements about what IS. These can be verified or falsified by reference to facts and data.

Examples:

• "The unemployment rate in Hong Kong was 3.2% in 2024."
• "A 10% increase in the price of petrol will reduce consumption by 3%."
• "If the government increases the minimum wage, employment will decrease."

Normative Economics

Normative economics deals with subjective, value-based statements about what OUGHT TO BE. These cannot be tested or verified; they involve opinions and judgements.

Examples:

• "The government should increase the minimum wage."
• "Inequality in Hong Kong is too high."
• "More resources should be allocated to healthcare."

Key Differences

Feature	Positive Economics	Normative Economics
Nature	Objective	Subjective
Testable?	Yes (can be verified by data)	No (involves value judgements)
Based on	Facts, data, logic	Opinions, values, ethics
Uses words	"Is", "will be"	"Should", "ought to"
Example	"Inflation is 5%."	"Inflation should be reduced."

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Economic Systems

Market Economy (Free Market Economy)

Definition: An economic system in which all decisions about production, consumption, and distribution are made by individuals and firms through the price mechanism, with minimal government intervention.

Characteristics:

• Private ownership of resources and means of production
• Decentralised decision-making (millions of individuals and firms make decisions)
• Price mechanism allocates resources (prices are determined by supply and demand)
• Profit motive drives production decisions
• Consumer sovereignty (consumers determine what is produced through their spending)

Advantages:

• Efficient allocation of resources (resources flow to their most valued use)
• Incentive for innovation and entrepreneurship (profit motive)
• Consumer choice and variety
• Responsive to changes in consumer preferences (price signals)
• Economic freedom

Disadvantages:

• Inequality in income and wealth distribution
• Under-provision of public goods (defence, street lighting)
• Over-production of demerit goods (tobacco, alcohol)
• Negative externalities (pollution, congestion)
• Monopoly power may develop
• No provision for the poor or disadvantaged

Command Economy (Planned Economy)

Definition: An economic system in which the government makes all decisions about production, consumption, and distribution.

Characteristics:

• State (government) ownership of resources and means of production
• Centralised decision-making (a central planning agency decides what, how, and for whom)
• Government sets prices and production targets
• Profit motive is not the driving force
• Production is based on government plans

Advantages:

• Can reduce inequality through planned redistribution
• Can direct resources to socially desirable goals (e.g., free education, healthcare)
• Can avoid unemployment (government can assign jobs)
• Can prevent over-production of demerit goods
• Can quickly mobilise resources for national priorities

Disadvantages:

• Inefficient allocation of resources (planners lack information about consumer preferences)
• Lack of incentive for innovation and hard work (no profit motive)
• Bureaucratic and slow decision-making
• Shortages and surpluses (planning errors)
• Lack of consumer choice
• Loss of economic freedom

Mixed Economy

Definition: An economic system that combines elements of both market and command economies. Most decisions are made by the market, but the government intervenes to correct market failures and achieve social objectives.

Characteristics:

• Both private and public ownership of resources
• Market forces determine most prices and production decisions
• Government intervenes through:
  • Taxation and subsidies
  • Provision of public goods (education, healthcare, infrastructure)
  • Regulation of monopolies and externalities
  • Welfare programmes (social security, minimum wage)
  • Price controls (rent control, minimum wage)

Hong Kong as a mixed economy:

Hong Kong is often described as one of the freest market economies in the world. It has:

• Free trade (no tariffs)
• Low taxation (simple tax system)
• Minimal government intervention
• Strong protection of property rights
• However, the government provides public housing, healthcare, and education

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Additional Concepts

Rationality

In economics, a rational decision-maker is one who:

1. Has clear preferences
2. Seeks to maximise utility (satisfaction) or profit
3. Makes consistent choices that achieve their objectives given their constraints

Marginal Analysis

Economists think at the margin -- they consider the additional (marginal) benefits and costs of a decision.

• Marginal Benefit (MB): The additional benefit from producing/consuming one more unit
• Marginal Cost (MC): The additional cost from producing/consuming one more unit

A rational decision-maker continues an activity as long as:

$\mathrm{MB} \gt \mathrm{MC}$

The optimal level is where:

$\mathrm{MB} = \mathrm{MC}$

Incentives

Incentives are factors that motivate or influence economic agents to act in a certain way.

• Positive incentives (rewards): Encourage an action (e.g., subsidies, tax breaks, higher wages)
• Negative incentives (penalties): Discourage an action (e.g., taxes, fines, regulations)

Price is the most important incentive in a market economy. Higher prices incentivise producers to supply more and consumers to buy less.

Economic vs Accounting Profit

	Accounting Profit	Economic Profit
Formula	Total Revenue - Explicit Costs	Total Revenue - (Explicit Costs + Implicit Costs)
Includes opportunity cost?	No	Yes
Relation	Economic profit = Accounting profit - Implicit costs

Implicit costs include the opportunity cost of the owner's time and capital. Economic profit is always less than or equal to accounting profit.

Ceteris Paribus

A Latin phrase meaning "all other things being equal." Economists use this assumption to isolate the effect of one variable on another, holding all other variables constant. For example, "an increase in price leads to a decrease in quantity demanded, ceteris paribus" -- meaning we assume no change in income, tastes, prices of other goods, etc.

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Common Pitfalls

1. Defining opportunity cost as "everything you give up": Opportunity cost is the value of the NEXT BEST alternative only, not the sum of all alternatives. If you choose A over B and C, and B is preferred to C, the opportunity cost of choosing A is B only.

2. Confusing PPC shifts with movements along the PPC: A movement along the PPC is caused by a reallocation of resources between the two goods. A shift of the PPC is caused by a change in the quantity or quality of resources or technology.

3. Stating that a point inside the PPC is efficient: A point inside the PPC indicates inefficiency (resources are not fully employed or are being used inefficiently). Only points ON the curve are efficient.

4. Confusing positive and normative statements: Any statement containing "should," "ought to," "fair," "unjust," or "too high/too low" is normative. Positive statements can be tested with data.

5. Saying free goods have no value: Free goods have no economic value (no opportunity cost and no price), but they may have value in use. The key distinction is that free goods are not scarce.

6. Equating mixed economy with equal parts market and command: A mixed economy is not necessarily a 50-50 combination. It refers to any economy that uses both market forces and government intervention. Hong Kong is a mixed economy despite being very market-oriented.

7. Ignoring the ceteris paribus assumption: When analysing economic relationships, always remember the ceteris paribus assumption. A change in demand, for instance, is caused by a change in non-price factors, holding the good's own price constant.

8. Confusing productive efficiency with allocative efficiency: Productive efficiency means producing at the lowest cost (on the PPC). Allocative efficiency means producing the right mix of goods (where P = MC). An economy can be productively efficient but not allocatively efficient.

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Practice Problems

Question 1: Opportunity Cost

A student has HKD 500 to spend. She can either buy a concert ticket (HKD 500) or a pair of shoes (HKD 500). She values the concert ticket at HKD 600 and the shoes at HKD 400.

(a) What is the opportunity cost of buying the concert ticket? (b) What is the opportunity cost of buying the shoes? (c) Which should she buy? Explain.

(a) The opportunity cost of buying the concert ticket is the value of the next best alternative forgone, which is the pair of shoes. Since she values the shoes at HKD 400, the opportunity cost is HKD 400.

(b) The opportunity cost of buying the shoes is the value of the next best alternative forgone, which is the concert ticket. Since she values the concert ticket at HKD 600, the opportunity cost is HKD 600.

(c) She should buy the concert ticket. The concert ticket provides HKD 600 of value for HKD 500 cost, giving a net benefit (consumer surplus) of HKD 600 - HKD 500 = HKD 100. The shoes provide HKD 400 of value for HKD 500 cost, giving a net benefit of HKD 400 - HKD 500 = -HKD 100 (a loss). A rational decision-maker maximises net benefit, so she should choose the concert ticket.

Question 2: PPC Calculation

An economy produces only two goods: food and clothing. The table below shows the maximum output of each good if all resources are devoted to it:

Good	Maximum Output
Food	200 units
Clothing	400 units

Assume constant opportunity cost (straight-line PPC).

(a) Draw the PPC and state its equation. (b) What is the opportunity cost of producing 1 unit of food? (c) If the economy is currently producing 100 units of food and 200 units of clothing, is this point on, inside, or outside the PPC? (d) What would cause the PPC to shift outward?

(a) The PPC is a straight line connecting (0, 400) on the clothing axis to (200, 0) on the food axis.

The equation of the PPC (with food on the x-axis and clothing on the y-axis):

Slope = $(0 - 400) / (200 - 0) = -2$

$C = 400 - 2F$

where F = food units and C = clothing units.

(b) The opportunity cost of producing 1 unit of food is 2 units of clothing (from the slope of the PPC). For every additional unit of food produced, 2 units of clothing must be given up.

(c) If F = 100, then the maximum clothing on the PPC = $400 - 2(100) = 200$ units. The economy is producing exactly on the PPC at this combination, so resources are fully and efficiently employed.

(d) The PPC would shift outward due to:

• An increase in the quantity of resources (more labour, capital, or land)
• An improvement in technology for producing food, clothing, or both
• An increase in the quality of resources (better education, improved health of workers)
• Discovery of new natural resources

Question 3: Positive vs Normative

Classify each of the following statements as positive or normative economics:

(a) "The inflation rate in Hong Kong was 2.5% last year." (b) "The government should increase spending on public housing." (c) "A rise in the minimum wage will increase unemployment." (d) "Income inequality in Hong Kong is unacceptable." (e) "If the government imposes a tax on carbon emissions, firms will produce less pollution." (f) "The GST (goods and services tax) is a better tax system than the current one."

(a) Positive -- it is a factual statement that can be verified with data. (b) Normative -- it uses "should" and reflects a value judgement about what the government ought to do. (c) Positive -- it is a testable hypothesis about cause and effect that can be examined with data. (d) Normative -- "unacceptable" is a value judgement; different people may have different views on what level of inequality is acceptable. (e) Positive -- it is a testable prediction about the effect of a policy change. (f) Normative -- "better" is a value judgement; it cannot be tested objectively without defining a criterion for "better."

Question 4: Economic Systems

Compare how a market economy and a command economy would answer the three fundamental economic questions.

What to produce?

• Market economy: Consumer demand determines what is produced. Producers respond to price signals. If demand for smartphones rises, their price increases, attracting more producers to the smartphone industry.
• Command economy: A central planning agency decides what goods and services to produce and in what quantities, based on government priorities rather than consumer preferences.

How to produce?

• Market economy: Producers choose the most cost-effective method of production. If labour is cheap, they use labour-intensive methods; if capital is cheap, they use capital-intensive methods. The goal is to minimise costs and maximise profit.
• Command economy: The government dictates the production methods. This may not be cost-effective if planners lack information about relative factor costs.

For whom to produce?

• Market economy: Goods are distributed to those who are willing and able to pay. Income distribution depends on the ownership of factors of production. Those with scarce skills or large capital holdings receive higher incomes and can buy more.
• Command economy: The government decides the distribution of output, often aiming for equal distribution or prioritising certain groups (e.g., party members, the military, workers in key industries).

Question 5: PPC with Increasing Opportunity Cost

An economy can produce capital goods and consumer goods. The following combinations are possible:

Combination	Capital Goods	Consumer Goods
A	0	500
B	50	480
C	100	440
D	150	370
E	200	260
F	250	0

(a) Calculate the opportunity cost of producing each additional 50 units of capital goods. (b) Why is the opportunity cost increasing? (c) If the economy is producing 100 capital goods and 300 consumer goods, what can you say about resource utilisation? (d) Explain how investing in capital goods now might affect the PPC in the future.

(a)

Movement	Capital Goods Increase	Consumer Goods Decrease	Opportunity Cost per 50 units of Capital
A to B	50	20	20 units of consumer goods
B to C	50	40	40 units of consumer goods
C to D	50	70	70 units of consumer goods
D to E	50	110	110 units of consumer goods
E to F	50	260	260 units of consumer goods

(b) The opportunity cost is increasing because resources are not equally efficient at producing both goods. Resources specialised in producing consumer goods (e.g., retail workers, consumer goods factories) are not well-suited to producing capital goods. As more and more resources are shifted from consumer goods to capital goods, the resources transferred are increasingly less efficient at producing capital goods, so more and more consumer goods must be sacrificed for each additional unit of capital goods.

(c) At 100 capital goods, the PPC allows a maximum of 440 consumer goods. The economy is producing only 300 consumer goods, which is inside the PPC. This means resources are either unemployed or being used inefficiently. The economy is experiencing underutilisation of resources (e.g., unemployment or idle factories).

(d) Investing in capital goods (e.g., building factories, improving technology) means producing fewer consumer goods today, but it increases the economy's productive capacity for the future. More and better capital goods mean that both capital goods and consumer goods can be produced in greater quantities in the future. This would cause the PPC to shift outward over time. An economy that invests heavily in capital goods will experience faster economic growth than one that focuses only on consumer goods.

Question 6: Specialisation and Trade

Country A can produce either 100 cars or 200 tonnes of wheat with all its resources. Country B can produce either 150 cars or 300 tonnes of wheat with all its resources.

(a) What is the opportunity cost of producing 1 car in each country? (b) Which country has a comparative advantage in producing cars? In producing wheat? (c) Should these countries specialise and trade? Explain.

(a)

Country A: Opportunity cost of 1 car = 200 / 100 = 2 tonnes of wheat

Country B: Opportunity cost of 1 car = 300 / 150 = 2 tonnes of wheat

Both countries have the same opportunity cost of producing cars. Neither has a comparative advantage.

(b) Since the opportunity costs are equal (2 tonnes of wheat per car in both countries), neither country has a comparative advantage in either good. Comparative advantage requires different opportunity costs.

(c) There is no basis for gains from specialisation and trade when opportunity costs are identical. Both countries face the same trade-off, so specialisation would not increase total output. Trade would be pointless unless other factors (transport costs, quality differences) are considered.

Note: This is a special case. In most DSE problems, opportunity costs will differ between countries, creating a basis for comparative advantage and gains from trade.

Question 7: Economic Profit vs Accounting Profit

A lawyer resigns from her job at a law firm where she earned HKD 600,000 per year. She opens her own law practice, using HKD 500,000 of her savings (which were earning 5% interest per year in a bank account) to set up the office. In her first year, her total revenue is HKD 1,000,000 and her explicit costs (rent, supplies, assistant's salary) total HKD 350,000.

(a) Calculate her accounting profit. (b) Calculate her economic profit. (c) Should she continue operating her own practice? Explain.

(a) Accounting profit = Total Revenue - Explicit Costs = 1,000,000 - 350,000 = HKD 650,000

(b) Economic profit = Total Revenue - Explicit Costs - Implicit Costs

Implicit costs:

• Foregone salary: HKD 600,000
• Foregone interest on savings: HKD 500,000 x 5% = HKD 25,000
• Total implicit costs = HKD 625,000

Economic profit = 1,000,000 - 350,000 - 625,000 = HKD 25,000

(c) Her economic profit is positive (HKD 25,000), which means she is earning more than her next best alternative. She is better off running her own practice than working at the law firm. She should continue operating her own practice.

However, the economic profit is very small relative to her accounting profit (HKD 25,000 vs HKD 650,000), so her opportunity cost is very high. If her revenue decreases or her costs increase slightly, her economic profit could become negative.

Question 8: Division of Labour and Productivity

A factory produces 100 chairs per day when each worker performs all stages of production. After introducing division of labour, each worker specialises in one stage. Output increases to 250 chairs per day. The factory employs 10 workers, each earning HKD 800 per day. The fixed costs are HKD 2,000 per day.

(a) Calculate labour productivity before and after division of labour. (b) Calculate the average cost per chair before and after division of labour. (c) If demand for chairs is only 150 per day, what is the implication of the division of labour?

(a) Labour productivity = Output / Number of workers

Before: $100 / 10 = 10$ chairs per worker per day

After: $250 / 10 = 25$ chairs per worker per day

Labour productivity has increased by 150% (from 10 to 25 chairs per worker per day).

(b) Total cost = Fixed costs + Variable costs (labour)

Before: Total cost = $2,000 + (10 \times 800) = 2,000 + 8,000 = 10,000$

Average cost per chair = $10,000 / 100 =$100 per chair

After: Total cost = $2,000 + (10 \times 800) = 10,000$ (labour cost unchanged; same workers, same pay)

Average cost per chair = $10,000 / 250 =$40 per chair

The average cost per chair has fallen from HKD 100 to HKD 40, a reduction of 60%. Division of labour has lowered average costs through increased productivity (economies of scale).

(c) If demand is only 150 chairs per day but the factory produces 250, there is excess supply of 100 chairs. This creates unsold inventory, which increases storage costs and ties up capital. The factory could either:

• Reduce the number of workers (but this may be difficult if workers are highly specialised)
• Reduce the workday or shifts
• Find new markets for the excess output

This illustrates a potential disadvantage of division of labour: overproduction when demand is limited, and the difficulty of adjusting highly specialised labour to changing market conditions.

Question 9: PPC Shift and Economic Growth

An economy produces only capital goods (K) and consumer goods (C). The PPC shifts outward such that the maximum output of K increases from 200 to 300 units, and the maximum output of C increases from 500 to 650 units. The economy was previously producing at point (100 K, 300 C).

(a) What could have caused the PPC to shift outward? (b) After the shift, is the old production point (100 K, 300 C) still on the new PPC? Explain. (c) Can the economy now produce 250 K and 400 C? Explain.

(a) The outward shift of the PPC could have been caused by:

• An increase in the quantity of factors of production (more labour, capital, or land)
• An improvement in technology (better production methods for one or both goods)
• An improvement in the quality of resources (better education and training of workers)
• Discovery of new natural resources
• Institutional improvements (better property rights, reduced corruption)

(b) After the shift, the maximum K is 300 and the maximum C is 650. The old point (100 K, 300 C) is well INSIDE the new PPC. With the new PPC, the economy can produce more of both goods. The old point is no longer on the frontier -- it represents underutilisation of the now-expanded resource base.

(c) We need to check whether (250 K, 400 C) is on or inside the new PPC. Assuming the PPC remains concave (increasing opportunity cost), we can check whether this combination is feasible.

The maximum K is 300 (with 0 C) and the maximum C is 650 (with 0 K). The point (250 K, 400 C) represents $250/300 = 83.3\%$ of maximum K and $400/650 = 61.5\%$ of maximum C.

Without knowing the exact shape of the new PPC, we cannot say with certainty whether this point is on or outside the curve. However, since the sum of these proportions (83.3% + 61.5% = 144.8%) exceeds 100%, this point may or may not be on the new PPC depending on the curvature. In a typical concave PPC, the point is likely to be feasible (inside or on the curve), because the increasing opportunity cost means the curve bows outward, allowing more of both goods to be produced than a straight line between the intercepts would suggest.

Question 10: Economic Systems and Resource Allocation

"Government intervention always improves economic outcomes." Evaluate this statement using economic concepts.

This statement is not correct. While government intervention can improve outcomes in certain situations, it can also worsen outcomes in others.

When government intervention IMPROVES outcomes:

• Public goods: The market under-provides public goods (e.g., defence, street lighting, lighthouses) because of the free-rider problem. Government provision ensures these goods are supplied.
• Externalities: The market over-produces goods with negative externalities (pollution) and under-produces goods with positive externalities (education, vaccination). Government can tax or subsidise to correct these market failures.
• Monopoly power: Unregulated monopolies can charge high prices and restrict output. Government regulation or antitrust laws can protect consumers.
• Information asymmetry: When buyers or sellers lack information (e.g., food safety, financial products), government regulation (labelling requirements, licensing) can protect consumers.
• Income redistribution: The market may result in unacceptable levels of inequality. Government can use progressive taxation and welfare programmes to redistribute income.

When government intervention WORSENS outcomes:

• Government failure: Government decisions may be influenced by political considerations rather than economic efficiency (e.g., subsidies to politically connected industries).
• Bureaucratic inefficiency: Government agencies may be slow, costly, and unresponsive compared to the private sector.
• Information problems: The government lacks the price signals and dispersed knowledge that markets use to allocate resources efficiently (the economic calculation problem).
• Unintended consequences: Price controls (e.g., rent control) may create shortages; minimum wages may cause unemployment; tariffs may trigger trade wars.
• Regulatory capture: Regulatory agencies may be captured by the industries they are supposed to regulate, serving industry interests rather than the public interest.
• Crowding out: Government borrowing to finance spending may raise interest rates, reducing private investment.

Conclusion: Government intervention improves outcomes when it corrects market failures, but it can create additional problems (government failures). The optimal level of intervention depends on the specific circumstances and the relative costs of market failure versus government failure. A mixed economy seeks to balance the efficiency of markets with targeted government intervention where needed.

Utility and Consumer Choice

Utility is the satisfaction or benefit that a consumer derives from consuming goods and services. It is a theoretical measure used to model consumer behaviour.

• Total utility (TU): The total satisfaction from consuming a given quantity of a good
• Marginal utility (MU): The additional satisfaction from consuming one more unit of a good

$\mathrm{MU} = \frac{\Delta \mathrm{TU}}{\Delta Q}$

Law of diminishing marginal utility: As a consumer consumes more units of a good, the additional satisfaction (marginal utility) from each additional unit decreases.

Units consumed	Total Utility	Marginal Utility
1	10	10
2	18	8
3	24	6
4	28	4
5	30	2
6	30	0
7	28	-2

The consumer maximises utility where the marginal utility per dollar spent is equal across all goods:

$\frac{\mathrm{MU}_A}{P_A} = \frac{\mathrm{MU}_B}{P_B}$

Consumer and Producer Surplus

Consumer surplus is the difference between the maximum price a consumer is willing to pay and the actual price they pay. It represents the benefit consumers receive from purchasing a good at a market price lower than their maximum willingness to pay.

$\mathrm{Consumer Surplus} = \mathrm{Maximum willingness to pay} - \mathrm{Actual price paid}$

On a demand and supply diagram, consumer surplus is the area below the demand curve and above the equilibrium price.

Producer surplus is the difference between the actual price a producer receives and the minimum price they are willing to accept. It represents the benefit producers receive from selling at a market price higher than their minimum acceptable price.

$\mathrm{Producer Surplus} = \mathrm{Actual price received} - \mathrm{Minimum acceptable price}$

On a demand and supply diagram, producer surplus is the area above the supply curve and below the equilibrium price.

Total surplus = Consumer surplus + Producer surplus. At market equilibrium, total surplus is maximised (allocative efficiency).

Market Failure

Market failure occurs when the free market fails to allocate resources efficiently, resulting in a loss of economic welfare.

Types of market failure:

1. Externalities: Costs or benefits that affect third parties not involved in the transaction

   • Negative externalities (e.g., pollution): Social cost > Private cost; over-production
   • Positive externalities (e.g., education, vaccination): Social benefit > Private benefit; under-production

2. Public goods: Goods that are non-excludable (cannot prevent non-payers from consuming) and non-rivalrous (one person's consumption does not reduce availability for others). The free rider problem leads to under-provision.

3. Information asymmetry: When one party has more information than the other (e.g., sellers know more about product quality than buyers). Leads to adverse selection and moral hazard.

4. Monopoly power: A single seller can restrict output and raise prices above the competitive level, causing deadweight loss.

5. Factor immobility: Resources (especially labour) may not move easily between industries or regions, causing structural unemployment.

6. Inequality: The market may result in an unacceptable distribution of income and wealth.

Government Intervention to Correct Market Failure

Market Failure	Government Intervention
Negative externalities	Taxation (Pigouvian tax), regulation, tradable permits
Positive externalities	Subsidies, direct provision (education, healthcare)
Public goods	Direct government provision, funded by taxation
Information asymmetry	Regulation (labelling, licensing), consumer protection laws
Monopoly power	Antitrust laws, price regulation, breaking up monopolies
Inequality	Progressive taxation, welfare programmes, minimum wage

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Problem Set

Problem 1: Opportunity Cost Calculation

A farmer has 10 hectares of land. She can grow rice (yielding 5 tonnes per hectare, selling at USD 400 per tonne) or maize (yielding 8 tonnes per hectare, selling at USD 250 per tonne).

(a) What is the opportunity cost of growing rice on 1 hectare? (b) Which crop should she specialise in? Explain.

Solution

(a) Revenue from 1 hectare of rice = 5 \times 400 = USD 2,000. Revenue from 1 hectare of maize = 8 \times 250 = USD 2,000. Opportunity cost of growing rice = USD 2,000 (maize revenue forgone).

(b) The opportunity costs are equal (both give USD 2,000 per hectare). She has no comparative advantage in either crop. Specialisation would not increase total revenue. She should split her land based on market conditions (prices, demand).

If you get this wrong, revise: Choice and Opportunity Cost

Problem 2: PPC Analysis

An economy can produce capital goods (K) and consumer goods (C). The following combinations are possible:

Combination	K	C
A	0	500
B	100	480
C	200	440
D	300	370
E	400	250
F	500	0

(a) Calculate the opportunity cost of each 100-unit increase in K. (b) Is the PPC concave or linear? Explain. (c) If the economy is at point D and a new technology doubles the productivity of the capital goods industry, what happens to the PPC?

Solution

(a) A to B: 20 C. B to C: 40 C. C to D: 70 C. D to E: 120 C. E to F: 250 C. The opportunity cost is increasing.

(b) The PPC is concave (bowed outward). The increasing opportunity cost confirms this. Resources are not equally efficient at producing both goods.

(c) The maximum K doubles from 500 to 1000. The PPC pivots outward on the C axis (the C intercept stays at 500). The economy can now produce more K for any given level of C, or more of both goods. This represents economic growth driven by technological progress in the capital goods sector.

If you get this wrong, revise: Production Possibility Curve (PPC)

Problem 3: Positive vs Normative Statements

Classify each statement as positive or normative:

(a) "Raising the minimum wage by 10% will reduce employment by 2%." (b) "The government should provide free university education for all citizens." (c) "Hong Kong's GDP grew by 3.2% last year." (d) "Income inequality in Hong Kong is too high and must be reduced." (e) "A depreciation of the HKD will increase the price of imports." (f) "The elderly should receive larger subsidies for healthcare."

Solution

(a) Positive -- testable hypothesis about cause and effect. (b) Normative -- uses "should" and reflects a value judgement. (c) Positive -- factual statement verifiable with data. (d) Normative -- "too high" is a value judgement. (e) Positive -- testable prediction about the effect of a policy change. (f) Normative -- uses "should" and reflects a value judgement.

If you get this wrong, revise: Positive vs Normative Economics

Problem 4: Economic and Accounting Profit

An engineer quits her job (salary: HKD 500,000/year) to start a software company. She invests HKD 800,000 of her savings (which earned 4% interest per year). In her first year: revenue = HKD 1,200,000, explicit costs (office rent, software licences, salaries of hired staff) = HKD 700,000.

(a) Calculate accounting profit. (b) Calculate economic profit. (c) Was starting the company a good decision?

Solution

(a) Accounting profit = 1,200,000 - 700,000 = HKD 500,000.

(b) Implicit costs: foregone salary = 500,000; foregone interest = 800,000 \times 4\% = 32,000. Total implicit costs = 532,000.

Economic profit = 1,200,000 - 700,000 - 532,000 = -32,000.

(c) Economic profit is negative (-32,000). Despite a positive accounting profit of 500,000, she is worse off than her best alternative (keeping her job and savings). She should return to her job unless she expects economic profit to become positive in future years.

If you get this wrong, revise: Economic vs Accounting Profit

Problem 5: Economic Systems Comparison

For each of the following decisions, explain how it would be made in (i) a market economy, (ii) a command economy, and (iii) a mixed economy:

(a) How many cars to produce (b) How to allocate healthcare resources (c) What wages to pay teachers

Solution

(a) Market: Consumer demand determines output. Firms produce where MR = MC. Command: A central planning agency sets production targets based on government priorities. Mixed: Market determines most output, but government may regulate (emission standards, safety requirements) or tax (excise duty).

(b) Market: Private hospitals provide healthcare based on ability to pay. Command: Government allocates all healthcare resources, determining who gets treatment. Mixed: Government provides basic healthcare (public hospitals), while private healthcare operates alongside for those willing to pay.

(c) Market: Wages are determined by supply and demand for teachers' skills. Command: Government sets all wages according to a national pay scale. Mixed: Public school teachers' wages are set by the government (with some negotiation); private school wages are determined by the market.

If you get this wrong, revise: Economic Systems

Problem 6: Marginal Analysis

A student is deciding how many hours to study for an exam. The table shows the marginal benefit (MB) and marginal cost (MC) of each additional hour:

Hour	MB (marks)	MC (marks)
1	25	5
2	20	8
3	15	12
4	10	17
5	5	23

(a) How many hours should the student study? (b) What is the total net benefit? (c) If the student studies 5 hours, what is the marginal net benefit of the 5th hour?

Solution

(a) The student should study as long as MB \gt MC.

Hour 1: MB=25 \gt MC=5 -- study. Hour 2: MB=20 \gt MC=8 -- study. Hour 3: MB=15 \gt MC=12 -- study. Hour 4: MB=10 \lt MC=17 -- do NOT study.

Optimal hours = 3.

(b) Total MB of 3 hours = 25 + 20 + 15 = 60. Total MC of 3 hours = 5 + 8 + 12 = 25. Net benefit = 60 - 25 = 35 marks.

(c) The 5th hour: marginal net benefit = MB - MC = 5 - 23 = -18 marks. The student loses 18 marks worth of benefit from studying the 5th hour (diminishing returns make additional study counterproductive).

If you get this wrong, revise: Marginal Analysis

Problem 7: Free Goods vs Economic Goods

For each of the following, state whether it is a free good or an economic good, and explain:

(a) Sea water at a beach (b) Bottled water at a convenience store (c) Sunlight in a desert (d) Clean air in a polluted city (e) Downloading a free software programme

Solution

(a) Free good (in most contexts) -- abundant, no price, zero opportunity cost. Note: in a desert, bottled seawater would be an economic good.

(b) Economic good -- scarce (limited supply at the store), positive price, positive opportunity cost.

(c) Free good -- abundant, no price. Even in a desert, sunlight is not scarce (though shade is).

(d) Economic good -- clean air is scarce in a polluted city. People pay for air purifiers and filters. Positive opportunity cost.

(e) Free good (for the downloader) -- no price, zero marginal cost of distribution. However, the software itself required resources to develop (the developer's time), so it is not a free good from society's perspective. This illustrates that whether something is "free" depends on the perspective.

If you get this wrong, revise: Free Goods vs Economic Goods

Problem 8: Division of Labour

A furniture factory employs 20 workers. Before division of labour, each worker performs all stages of production and produces 2 chairs per day (total: 40 chairs). After division of labour, each worker specialises in one stage and output rises to 5 chairs per worker per day (total: 100 chairs).

(a) Calculate the percentage increase in labour productivity. (b) What are three advantages of this division of labour for the factory owner? (c) What are two potential disadvantages for the workers?

Solution

(a) Before: 40/20 = 2 chairs per worker. After: 100/20 = 5 chairs per worker. Productivity increase = (5-2)/2 \times 100\% = 150\%.

(b) Advantages for the owner:

• Higher total output (100 vs 40) at the same labour cost
• Lower average cost per chair (same total wage / more chairs)
• Faster production (workers become skilled at their specific task)
• Easier to replace absent workers (simplified tasks)

(c) Disadvantages for workers:

• Monotony and boredom from repetitive tasks
• Vulnerability to unemployment (easier to replace specialised workers)
• Less job satisfaction and sense of accomplishment
• If demand falls, highly specialised workers cannot easily switch jobs

If you get this wrong, revise: Division of Labour

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Extended Problem Set: Advanced Basic Economic Concepts

Problem 9: PPC and Economic Growth

A country's PPC for capital goods ($K$) and consumer goods ($C$) is given by $K = 400 - C - 0.005C^2$, where $0 \le C \le 200$. Currently producing at $C = 100$, $K = 250$.

(a) Verify that $(100, 250)$ lies on the PPC. (b) Calculate the opportunity cost of producing the 101st unit of consumer goods. (c) If the country invests in new technology, shifting the PPC outward to $K = 480 - C - 0.005C^2$, by how much does the maximum possible output of each good increase? (d) Explain why the PPC is concave and relate this to the concept of increasing opportunity cost using a Hong Kong example.

Solution

(a) At $C = 100$: $K = 400 - 100 - 0.005(10000) = 400 - 100 - 50 = 250$. Verified.

(b) The marginal rate of transformation (opportunity cost) is $MRT = \left|\frac{dK}{dC}\right| = |{-1 - 0.01C}| = 1 + 0.01C$.

At $C = 100$: $MRT = 1 + 1 = 2$. The 101st unit of consumer goods costs 2 units of capital goods in opportunity cost.

(c) New PPC intercept: when $C = 0$, $K = 480$. When $K = 0$: $0 = 480 - C - 0.005C^2$. $0.005C^2 + C - 480 = 0$. $C = \frac{-1 + \sqrt{1 + 9.6}}{0.01} = \frac{-1 + \sqrt{10.6}}{0.01} = \frac{-1 + 3.256}{0.01} = 225.6$.

Maximum capital goods: $400 \to 480$ (increase of 80 units, 20%). Maximum consumer goods: $200 \to 225.6$ (increase of 25.6 units, 12.8%).

(d) The PPC is concave because resources are not perfectly adaptable to producing both goods. As the economy shifts resources from capital goods to consumer goods, it must first use resources best suited to consumer goods production (low opportunity cost). As it continues shifting, it must use resources increasingly less suited to consumer goods (high opportunity cost). This is the law of increasing opportunity cost.

Hong Kong example: In the 1970s, Hong Kong shifted resources from manufacturing to services. Initially, workers in low-skill assembly could be retrained for service jobs relatively easily (low opportunity cost). As the shift continued, the remaining manufacturing workers had skills very specific to manufacturing (e.g., textile machine operators) that were harder to transfer to services, requiring more retraining and creating higher opportunity costs.

If you get this wrong, revise: PPC and Opportunity Cost

Problem 10: Mixed Economy -- Government Intervention in Hong Kong Housing

Hong Kong's housing market has the following characteristics: average flat price $=$HK$6$ million, median household income $=$HK$27,500/month, price-to-income ratio$= 18.2$(one of the highest in the world). The government provides public rental housing (PRH) to 30$HK$2,000/month.

(a) Calculate how many months of income are needed to buy an average flat. (b) Explain the market failure that justifies government provision of public housing. (c) Calculate the implicit subsidy received by a PRH household if the market rent for an equivalent flat is $HK$15,000/month. (d) Evaluate whether expanding public housing is the best solution to Hong Kong's affordability crisis.

Solution

(a) Months of income $= 6\,000\,000 / 27\,500 = 218$ months $= 18.2$ years. This assumes the household saves 100% of income, which is impossible. With a 50% savings rate, it would take 36.4 years.

(b) The market failures justifying government intervention in housing:

1. Positive externalities: Adequate housing improves health outcomes, educational attainment, and productivity. These benefits accrue to society, not just the homeowner, meaning the private market underprovides housing relative to the social optimum.

2. Equity concern (not strictly a market failure): Housing is a basic necessity. The market allocates housing based on willingness to pay, which is correlated with income. Low-income households cannot afford adequate housing even though the social benefit of housing them exceeds the private cost. This is a merit good argument.

3. Land market imperfections: Hong Kong's land supply is controlled by the government, and the land market is subject to speculation and oligopolistic practices by major developers. The resulting high land prices distort the housing market, creating a market failure.

4. Information asymmetry: Quality and safety standards in housing are difficult for individual buyers/renters to assess, creating a role for government regulation (building codes, safety inspections).

(c) Implicit monthly subsidy = 15\,000 - 2\,000 = \text{HK}\13,000$.

Annual subsidy = 13\,000 \times 12 = \text{HK}\156,000$.

With approximately 2 million PRH residents (30% of 7.5 million population, ~700,000 households): total annual subsidy = 700\,000 \times 156\,000 = \text{HK}\109.2$ billion. This is a substantial fiscal commitment.

(d) Evaluation:

Arguments for expanding PRH:

• Provides immediate relief for low-income households who cannot afford private housing.
• The long waiting list (average 5.5 years) indicates significant unmet demand.
• Reduces income inequality and improves social mobility.

Arguments against relying solely on PRH:

• Long construction lag (5--10 years from planning to completion).
• Concentrates low-income households in specific estates, potentially creating social segregation.
• Does not address the root cause (high land prices).
• Large fiscal burden.

Alternative/complementary approaches:

• Increase land supply to reduce the equilibrium price of private housing.
• Starter homes / subsidised homeownership (Home Ownership Scheme).
• Rent control (with caveats about quality deterioration).
• Mortgage interest deduction (though this may inflate prices).

A comprehensive approach combining supply-side reform (land release) with targeted demand-side support (HOS, PRH) is likely more effective than any single policy.

If you get this wrong, revise: Economic Systems and Government Intervention

Problem 11: Specialisation and Trade with Unequal Country Sizes

Country A (large) can produce 1000 wheat or 500 cloth. Country B (small) can produce 100 wheat or 400 cloth.

(a) Calculate opportunity costs and identify comparative advantages. (b) If they specialise and trade at 1 wheat $= 0.8$ cloth, show gains from trade. (c) What happens if Country B is so small that its entire production is insufficient to meet Country A's import demand? Does trade still benefit both? (d) Relate this to the Hong Kong-mainland China trade relationship.

Solution

(a) Opportunity cost of 1 wheat:

• Country A: $500/1000 = 0.5$ cloth.
• Country B: $400/100 = 4$ cloth.

Country A has a comparative advantage in wheat (lower opportunity cost: 0.5 vs 4). Country B has a comparative advantage in cloth (opportunity cost of 1 cloth: A $= 2$ wheat, B $= 0.25$ wheat).

(b) Without trade (50/50 split): A produces 500 wheat, 250 cloth. B produces 50 wheat, 200 cloth. World: 550 wheat, 450 cloth.

With specialisation: A produces 1000 wheat, 0 cloth. B produces 0 wheat, 400 cloth. World: 1000 wheat, 400 cloth.

At 1 wheat $= 0.8$ cloth: If A exports 200 wheat to B for 160 cloth: A consumes 800 wheat, 160 cloth (gains: +300 wheat, -90 cloth). B consumes 200 wheat, 240 cloth (gains: +150 wheat, +40 cloth). Both gain.

(c) If A wants to import 500 cloth (half its pre-trade consumption), B can only supply 400 cloth (its entire capacity). In this case, trade is limited by B's capacity. B specialises fully in cloth (400 units), A partially specialises (produces some cloth itself).

A produces 600 wheat, 200 cloth (not fully specialised). Trade: A exports 100 wheat for 80 cloth. A consumes 500 wheat, 280 cloth. B consumes 100 wheat, 320 cloth. Both still gain compared to autarky, but the gains are smaller than in part (b) because B's small size limits the extent of specialisation and trade.

(d) Hong Kong-mainland China: This is analogous to the A-B relationship. China (Country A) is vast, while Hong Kong (Country B) is tiny. Hong Kong cannot supply all of China's import needs (food, raw materials, consumer goods). However, Hong Kong specialises in high-value services (finance, logistics, professional services) where its comparative advantage is strongest. China's demand for these services far exceeds what Hong Kong can supply, so Hong Kong operates at full capacity, and both gain from trade. The key insight is that even a very small economy can benefit enormously from trade with a large one, as long as it specialises according to comparative advantage.

If you get this wrong, revise: Specialisation and Trade

Problem 12: Opportunity Cost in Everyday Decision-Making

A university student in Hong Kong has the following options for the summer:

• Option A: Internship at a bank, paying HK$15,000/month for 2 months.
• Option B: Summer school, costing HK$30,000 in tuition, but the course will increase starting salary by HK$5,000/month for the first 3 years of employment.
• Option C: Travel and leisure, valued by the student at HK$20,000 in utility.

The student's discount rate is 6% per annum. The student graduates in one year and expects to work for 3 years after graduation before pursuing further studies.

(a) Calculate the net present value of each option. (b) Which option has the highest NPV? What is the opportunity cost of choosing it? (c) How would the analysis change if the student expects to work for 10 years after graduation? (d) Explain why the concept of opportunity cost is central to rational decision-making.

Solution

(a) Option A (Internship): NPV = 15\,000 \times 2 = \text{HK}\30,000$.

Option B (Summer school): Cost $= 30\,000$. Benefit $= 5\,000/month \times 36$ months $= 180\,000$ (nominal), but this starts one year from now.

NPV of benefits $= \sum_{t=13}^{48} \frac{5000}{(1.005)^t}$ where the monthly discount rate $= 0.5\%$.

Approximation: annual discount rate $= 6\%$. PV of annuity of 3 years starting in 1 year $= \frac{5000 \times 12}{0.06} \times \frac{1 - 1.06^{-3}}{1.06} = \frac{60\,000}{0.06} \times \frac{1 - 0.8396}{1.06} = 1\,000\,000 \times 0.1515 = 151\,500$.

NPV of Option B = 151\,500 - 30\,000 = \text{HK}\121,500$.

Option C (Travel): NPV = \text{HK}\20,000$.

(b) Option B has the highest NPV (HK$121,500). The opportunity cost of choosing Option B is the next best alternative: Option A with NPV of HK$30,000. (The opportunity cost is the foregone value, not the cost of the chosen option.)

(c) With 10 years of work: PV of benefits $= \frac{60\,000}{0.06} \times \frac{1 - 1.06^{-10}}{1.06} = 1\,000\,000 \times \frac{1 - 0.5584}{1.06} = 1\,000\,000 \times 0.4183 = 418\,300$.

NPV of Option B = 418\,300 - 30\,000 = \text{HK}\388,300$.

Option B becomes even more attractive with a longer working horizon because the salary increase compounds over more years.

(d) Opportunity cost is central to rational decision-making because it forces the decision-maker to consider the full cost of a choice, including the value of the best alternative forgone. Without considering opportunity cost, the student might think Option B "costs" only HK$30,000 (the tuition fee). But the true cost includes the HK$30,000 in foregone internship earnings. Rational decision-making requires comparing the net benefits of all alternatives (benefits minus all costs, including opportunity costs) and choosing the one with the highest net benefit. This principle applies to all economic decisions: individual consumption, firm production, government policy, and international trade.

If you get this wrong, revise: Opportunity Cost