According to the graph, as the economy moves from producing 10 guns to

According to the graph, as the economy moves from producing 10 guns to 20 guns, to 30 guns, to 40 guns, etc., the production of guns is increasing by 10 guns. What happens to the opportunity cost of producing an additional 10 guns as the economy moves south-east on the production possibilities frontier? a. it remains constant b. it decreases c. it increases d. it increases and then decreases

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