Division S Sells Its Product to Unrelated Parties at a Price

Essay

Division S sells its product to unrelated parties at a price of $20 per unit. It incurs variable costs of $7 per unit and has fixed costs of $50,000 per month. Monthly production is generally 10,000 units.
Division B uses Division S's product in its operations. It can purchase the units from Division S at $20 per unit but must pay $1.50 per unit in shipping costs. Alternatively, Division B can buy from Division S's competition at a delivered price of $21 per unit.
Required:
(a) From the company's perspective, should Division B purchase the units internally or externally? Assume Division S has ample capacity to handle all of Division B's needs.
(b) Would your answer change if Division S can sell everything it produces to outside customers?