Two electric motors (A and B) are being considered to drive a centrifugal pump. One of the motors must be selected. Each motor is capable of delivering 60 horsepower (output) to the pumping operation. It is expected that the motors will be in use 800 hours per year. At the end of their useful lives, both motors will have negligible salvage values. An 10 % annual

MARR and the repeatability assumption are applicable. Electricity costs $0.07 per kilowatt-hour. (Recall, I hp = 0.746 kW.)

Which motor should be selected using a present worth comparison?

A Initial cost (S) 1200 Annual maintenance cost (S) 160 Useful Life (years) 3 Electrical efficiency (%) 90 Motor B 1000 175 5 80