Lincoln Company produces a part that is used in the manufacture of one of its products $.$ The unit manufacturing costs of this part, assuming a production level of $5,000$ units $,$ are as follows : Direct material $$6$ Direct labor $5$ Variable manufacturing $4$ overhead Fixed manufacturing overhead Total cost $ $14$ Erickson Company has offered to sell $5,000$ units of the same part to Lincoln Company for $$13$ per unit. Assuming the company has no other use for its facilities and that the fixed manufacturing costs are unavoidable $,$ what should Lincoln Company do$?$ Make the part and save $$1$ per unit $.$ Make the part and save $$2$ per unit. Buy from Erickson and save $$1$ per unit. Buy from Erickson and save $$2$ per unit $.$