Joe spends all of his money on concert tickets and CDs. If Joe's income is $100, the price of tickets is $20 and the price of CDs is $10, his possible consumption bundles would look like those in the following table:

Quantity of Tickets Quantity of CDs

50

4 2

3 4

2 6

18

010

If he is currently pruchasing 3 tickets, but would like to purchase a 4th ticket, what would be his opportunity cost in terms of CDs of getting one more ticket?

Select one:

a.$20

b.2 CDs

c.4 CDs

d.$10

e.1 CD