Trade gains from full specialization in cars Steps:

• Specialize in cars to reach maximum production on PPC: 1000 cars.
• Export all 1000 cars at terms of trade: 4 cars per 1 truck.
• Import trucks: 1000 cars ÷ 4 = 250 trucks.
• Domestic market gains 250 extra trucks compared to autarky at point X.

Why A is correct:

• Matches exact import calculation from full car export using given 4:1 terms of trade.

Why the others are wrong:

• B: Assumes 6000 cars produced/exported, exceeding PPC maximum.
• C: Assumes 1:1 trade ratio or 4000 cars, ignoring 4:1 terms.
• D: Assumes 2:1 ratio or 8000 cars, inconsistent with terms and PPC.

Final answer: A