People come from all around to catch fish to sell

Subject: General Questions    / General General Questions
Question
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?