[기출문제] 세종대 경제원론 2025-2 중간 기출문제 (정답 포함)

1. b) Complete the project because the marginal benefit ($3M) is greater than the marginal cost ($1M).
   * Rationale: Rational people think at the margin (Principle 3). The $5M is a sunk cost and irrelevant. The marginal cost to finish is $1M, and the marginal benefit is the $3M in expected sales. Since $3M > $1M, they should finish.

2. b) The government should impose a price ceiling on gasoline to protect low-income households.
   * Rationale: This is a normative statement because it prescribes what should be done (a value judgment). The other options are positive statements, as they describe what happens (testable claims).

3. d) Increasing opportunity costs as more of one good is produced.
   * Rationale: A bowed-out shape means the slope of the PPF (which represents opportunity cost) gets steeper as you move along the x-axis, indicating you must give up more and more of the y-axis good to get one more unit of the x-axis good.

4. c) Germany has an absolute advantage in both goods, and both countries have the same opportunity cost for cars.
   * Rationale: Germany has an absolute advantage (less labor) in both.
   * Opp. Cost of 1 Car (Germany) = 400 hours / 2 hours/wine = 200 wine.
   * Opp. Cost of 1 Car (France) = 600 hours / 3 hours/wine = 200 wine.
   * Because the opportunity costs are identical, there is no basis for comparative advantage and no gains from trade are possible.

5. c) 200 cases of wine.
   * Rationale: Opp. Cost of 1 Car (Germany) = (Time for 1 Car) / (Time for 1 Wine) = 400 hours / 2 hours = 200.

6. a) Price increases, Quantity increases.
   * Rationale: An increase in income shifts the demand curve for a normal good to the right. This leads to a higher equilibrium price and a higher equilibrium quantity.

7. d) Quantity will fall, and the effect on price is ambiguous.
   * Rationale:
     * Steel price increase (input cost) → Supply shifts left.
     * Income fall (normal good) → Demand shifts left.
     * When both S and D shift left, Quantity must fall. However, the price effect is ambiguous (S-shift pulls P up, D-shift pulls P down).

8. a) Total revenue will increase.
   * Rationale: When demand is inelastic (PED < 1), a price increase leads to a proportionally smaller decrease in quantity. Therefore, total revenue (P \times Q) increases.

9. b) The shortage of housing will worsen as the supply of apartments becomes more elastic.
   * Rationale: In the long run, both supply (landlords won't build/maintain) and demand (more people will try to move in) become more elastic, making the gap between Q^D and Q^S even larger.

10. b) Consumers will bear most of the burden.
   * Rationale: The tax burden falls more heavily on the side of the market that is less elastic (less responsive to price). Since demand is inelastic, consumers cannot easily reduce their consumption and will absorb most of the price increase.

11. Short Answer Model Answers
 * Efficiency refers to maximizing the total economic pie (total output/surplus). Equality refers to how that pie is distributed among society's members. A highly progressive income tax increases equality by taking a larger share from high-income earners and (often) redistributing it to low-income earners. However, this policy can reduce efficiency (shrink the pie) because the high tax rates on high-income earners may reduce their incentive to work hard, invest, and innovate.

12.
   a.  [A correct PPF graph is drawn, bowed-outward, axes labeled "Education" and "Consumer Goods"]
   b.  Point A is drawn anywhere inside the PPF curve.
   c.  Point B is drawn anywhere outside the PPF curve.
   d.  The PPF pivots outward along the "Education" axis, while the "Consumer Goods" intercept remains the same.

13. a.  Absolute Advantage: U.S. in computers (20 > 10) and U.S. in shirts (100 > 80).
   b.  Opportunity Cost (1 Computer):
   * U.S.: 100 Shirts / 20 Computers = 5 Shirts
   * China: 80 Shirts / 10 Computers = 8 Shirts
   c.  Comparative Advantage: The U.S. has the comparative advantage in computers because its opportunity cost (5 shirts) is lower than China's (8 shirts).
   d.  Terms of Trade: A mutually beneficial price for 1 computer must lie between 5 shirts and 8 shirts (e.g., 1 computer for 6 shirts, or 1 computer for 7 shirts).

14. A decrease in the price of hot dogs (a complement) will increase the demand for ketchup.
   * The demand curve for ketchup shifts to the right (from D_1 to D_2).
   * This results in a higher equilibrium price (P_2) and a higher equilibrium quantity (Q_2) for ketchup.
 

15. a.  Equilibrium: Set Q^D = Q^S → 300 - P = 2P → 300 = 3P → P = 100.
   * Plug P back in: Q = 2(100) → Q = 200.
   b.  Price Floor at $120: A price floor is a minimum price. Since $120 > $100 (equilibrium), the floor is binding.
   * At P = 120:
   * Q^D = 300 - 120 = 180
   * Q^S = 2(120) = 240
   * Result: A Surplus of Q^S - Q^D = 240 - 180 = \mathbf{60} units.
 

16. a.  PED (Midpoint):
   * %ΔQ = (600 - 800) / ((600 + 800) / 2) = -200 / 700 ≈ -28.57%
   * %ΔP = (250 - 200) / ((250 + 200) / 2) = 50 / 225 ≈ +22.22%
   * PED = | %ΔQ / %ΔP | = | -28.57% / 22.22% | ≈ 1.29
   b.  Since the elasticity (1.29) is greater than 1, demand is elastic.
   c.  Total Revenue (TR) Change:
   * TR (old) = P_1 \times Q_1 = \$200 \times 800 = \$160,000
   * TR (new) = P_2 \times Q_2 = \$250 \times 600 = \$150,000
   * Total revenue decreased by $10,000 (which is expected when price rises on elastic demand).

17. The PED for Rolex watches is higher (more elastic) because:
   * Luxuries vs. Necessities: A Rolex is a luxury good. A price increase will cause consumers to easily forgo the purchase. Insulin is a necessity for diabetics; they must buy it regardless of the price.
   * Availability of Substitutes: Rolex has many substitutes (other watch brands, or no watch at all). Life-saving insulin has no close substitutes.

18. a.  Income Elasticity (Midpoint):
   * %ΔQ = (15 - 20) / ((15 + 20) / 2) = -5 / 17.5 ≈ -28.57%
   * %ΔI = (50,000 - 40,000) / ((50,000 + 40,000) / 2) = 10,000 / 45,000 ≈ +22.22%
   * Income Elasticity = %ΔQ / %ΔI = -28.57% / 22.22% ≈ -1.29
   b.  Because the income elasticity is negative, instant noodles are an inferior good for this person.
 

19. a/b/c/d. The graph should show the supply curve shifting upward by the $2 tax amount (from S_1 to S_2).
   * The new intersection (of S_2 and D_1) determines Q_2 (which is lower than Q_1) and P_C (which is higher than P_1).
   * P_P is found by dropping down from the new intersection to the old supply curve (S_1). P_P is lower than P_1.
   e.  The tax revenue is a rectangle with a height equal to the tax (P_C - P_P = \$2) and a width equal to the new quantity (Q_2).

20. Economic incidence (who really pays) is determined by the relative elasticities of supply and demand, not by who legally pays the tax. The tax creates a $2 "wedge" between the price buyers pay and the price sellers receive.
   * Because producers must now pay the $2 tax, they will supply less at every price, shifting the supply curve up.
   * This shift forces a new, higher equilibrium price (P_C) for consumers. So, consumers pay part of the tax (the P_C - P_1 amount).
   * Producers also receive a lower price after paying the tax (P_P) than they did before (P_1). So, producers also pay part of the tax (the P_1 - P_P amount).
   * The burden is shared by both.