Use the following to answer question 7:

Question

Point Bread Tractor

A 20 0

B 18 1

C 14 2

D 8 3

E 0 4

Refer to the above schedule. Starting at point A, the opportunity cost of producing each successive unit of tractors is:

a constant 2 units of bread
8, 6, 4, and 2 units of bread
2, 4, 6, and 8 units of bread
D) the reciprocal of the output of tractors