Suppose that you have a choice of working during the summer or taking summer classes. Summer tuition and books are $2,000. If you work, you could make $10,000. Your rent is $4,000 for the summer, regardless of your choice. The opportunity cost of going to summer school is therefore equal to:_________.
a. $14,000
b. $12,000
c. $2,000
d. $10,000