Two electric motors (C and D) are being considered to drive a bulk conveyor. One of the motors must be selected. Each motor is capable of delivering 50 horsepower (output) to the conveyor operation. It is expected that the motors will be used 1,000 hours per year. At the end of their useful lives, both motors will have negligible salvage values. An 8% MARR and the repeatability assumptions hold. Electricity costs $0.085 per kilowatt-hour. (Recall, I hp = 0.746 kW)

1. On the basis of the data shown in the accompanying table and using an annual worth comparison, which motor should be selected?

2. What basic tradeoff is being made in this problem?

Initial cost (S) 1100 Annual maintenance cost (S) 150 Useful Life (years) 5 Electrical efficiency (%) 82 Motor D 950 100 15 62 Initial cost (S) 1100 Annual maintenance cost (S) 150 Useful Life (years) 5 Electrical efficiency (%) 82 Motor D 950 100 15 62