Garett Engines Ltd$.($GEL$)$ manufactures a variety of engines for use in heavy equipment. The company has always produced all of the necessary parts for its engines, including all of the oil pumps. An outside supplier has offered to produce and sell one type of oil pump to GEL for a cost of $$43$ per unit. To evaluate this offer, GEL has gathered the following information relating to its cost of producing $15,800$ oil pumps: