If n is the number of fishermen in the river, then each fisherman catches 10 + 120/n kg of fish each day (depending on how many fishermen there are). A kg of fish sells for 5 pounds, a fishing license costs 20 pounds, and a fisherman could also work at the docks for 80 pounds a day. How many fishermen will fish in the river each day? (a) 8 (b) 12 (c) 16 (d) 18 (e) 20