Figure 6-1 Income = $ 100

Figure 6-1
Income = $ 100
Price per Ticket = $20
Price per Compact Disk $ 10

-Joe spends all of his money on concert tickets and compact disks.Figure 6-1 shows his budget constraint when his income is $100.The price of a ticket is $20,while the price of a compact disk is $10.If Joe currently buys 3 tickets and would like to purchase a fourth,his opportunity cost would be

A) 1 compact disk
B) $20
C) $10
D) 2 compact disks
E) 4 compact disks