6-20. Two electric motors (A and B) are being considered to drive a centrifugal pump. Each motor is capable of delivering 50 horsepower (output) to the pumping operation. It is expected that the motors will be in use 1,000 hours per year. If electricity costs $0.07 per kilowatt-hour and 1 hp = 0.746 kW, which motor should be selected if MARR = 8% per year? Refer to the data below. (6.4)

Motor A Motor B Initial cost $1,200 $1,000 Electrical efficiency 0.82 0.77 Annual maintenance $60 $100 Life 5 years 5 years