11-6. An area can be irrigated by pumping water from a nearby river. Two competing installations are being considered.

Pump A Pump B 6 in. System 8 in. System Operating load on motor 15 hp 10 hp Efficiency of pump motor 0.60 0.75 Cost of installation $2,140 $4,280 Market values at the end $60 $0 of useful life Useful life 9 years 9 years The MARR is 10% per year and electric power for the pumps costs $0.06 per kWh. Recall that 1 horsepower (hp)

equals 0.746 kilowatts. (11.2, 11.3)

a. At what level of operation (hours per year) would you be indifferent between the two pumping systems?

If the pumping system is expected to operate 2,000 hours per year, which system should be recommended?

b. Assuming 2,000 hours of operation, perform a sensitivity analysis on the efficiency of Pump A. Over what range of pumping efficiency is Pump A preferred to Pump B?