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 apples?

A) 0.5 of a kilogram of bananas
B) 5/12 of a kilogram of bananas
C) 2 kilograms of bananas
D) 2 kilograms of apples
E) 100 kilograms of bananas