Opportunity Cost via PPC Slope

Steps:

• Opportunity cost of cars is trucks forgone per additional car, measured by the PPC's slope magnitude.
• Examine each economy's PPC slope where production shifts from trucks to cars.
• Identify the flattest slope (smallest absolute value) among A, B, C, D.
• Select the economy with that slope for lowest opportunity cost.

Why A is correct:

• Economy A's PPC has the shallowest slope, per the law of increasing opportunity costs, sacrificing fewest trucks per car.

Why the others are wrong:

• B: Steeper slope than A, higher trucks forgone per car.
• C: Even steeper slope, increasing opportunity cost further.
• D: Steepest slope, highest opportunity cost for cars.

Final answer: A