Suppose a Fishing Boat Currently Brings 10,000 Fish to Market

Suppose a fishing boat currently brings 10,000 fish to market and earns a profit of$40,000 when the price of fish is $8. Suppose the boat dealer had overcharged the boat owner for the boat and refunded the overcharged amount. If the profit increases to $7.50per fish, what was the value of the refund from the dealer?

A) $2.50
B) $25,000
C) $3.50
D) $35,000
E) $75,000