It is calculated that the annual sales of an energy saving device will be 20,000 the first year and increase by 10,000 per year until 50,000 units are sold during the fourth year. Proposal A is to purchase manufacturing equipment costing $120,000 with an estimated salvage value of $15,000 at the end of 4 years. Proposal B is to purchase equipment costing $280,000 with an estimated salvage value of $32,000 at the end of 4 years. The variable manufacturing cost per unit under proposal A is calculated to be $8, 00, but is calculated to be only $2.60 under proposal B. If the interest rate is 9%, discuss which proposal should be accepted for a 4-year production horizon?