The value of a fishery depends on the number of people using it. The total value function is

v(f)=8000f5f^2

.

The marginal cost per fisher is $100.

Suppose the government wants to ensure that the fishery is used optimally (that is, that the number of people using the fishery equals the socially optimal number). To meet its goal, the government is imposing a license fee to use the fishery. The appropriate license fee is