Farmer Jones and Farmer Smith graze their cattle on the same field. If there are 20 cows grazing in the field each cow produces each cow produces $4000 of milk. If there are more cows in the field, then each cow can eat less grass and the milk production falls. With 30 cows on the field each produces $3000 of milk; with 40 cows each produces $2000 of milk. Cows cost $1000 apiece. Assume that Farmer Jones and farmer Smith can buy either 10 cows or 20 cows; find out the Nash equilibrium and represent the same formal language