On a Production Possibilities Frontier,500 Kilograms of Apples and 1200

On a production possibilities frontier,500 kilograms of apples and 1200 kilograms of bananas can be produced while,at another point on the same frontier,300 kilograms of apples and 1300 kilograms of bananas can be produced.Between these points,what is the opportunity cost of producing a kilogram of bananas?

A) 200 kilograms of apples
B) 12/5 = 2.4 kilograms of apples
C) 2 kilograms of apples
D) 0.5 a kilogram of apples
E) 2 kilograms of bananas