Suppose Al, Betty, and Carl Own the Only Fishing Companies

Suppose Al, Betty, and Carl own the only fishing companies in your village. Suppose the market price today is $10 per fish. Suppose Al catches 4,000 fish with an average totalcost of $7.50, Betty catches 6,000 fish with an average total cost of $6, and Carl catches10,000 fish with an average total cost of $7. How much would Betty's average total cost have to fall in order for her to make as much total profit as Carl?

A) $1
B) $2
C) $4
D) $5
E) Betty cannot make as much profit as Carl with only 6,000 fish.