At the Santa Barbara fishing hole, people come from all around to catch fish to sell at the fish market.The total number of fish caught is F= 10x−x2 where x is the number of fishermen. Suppose it costs each person $20 a day to fish and that fish sell for $10 each at the market. At the social optimum,how much would it hurt all the other fishermen (combined) if one more person started fishing?
(a) $30
(b) $20
(c) $10
(d) $40