Two 150-horsepower (HP) motors are being considered for installation at a municipal sewage-treatment plant.
The first motor costs $4,500 and has an operating efficiency of 83% at full load. The second motor costs $3,600
and has an efficiency rating of 80% at full load. Both motors are projected to have zero salvage value after a life
of 10 years. The annual operating and maintenance cost (excepting power cost) amounts to 15% of the original
cost of each motor. The power costs are a flat 5 cents per kilowatt-hour. Determine the minimum number of
hours of full-load operation per year necessary to justify the purchase of the more expensive motor at i = 6%.

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The Answer of Two 150-horsepower (HP) motors are being considered for installation at a municipal sewage-treatment plant.
The first motor costs $4,500 and has an operating efficiency of 83% at full load. The second motor costs $3,600
and has an efficiency rating of 80% at full load. Both motors are projected to have zero salvage value after a life
of 10 years. The annual operating and maintenance cost (excepting power cost) amounts to 15% of the original
cost of each motor. The power costs are a flat 5 cents per kilowatt-hour. Determine the minimum number of
hours of full-load operation per year necessary to justify the purchase of the more expensive motor at i = 6%.

Two 150-Horsepower (HP) Motors Are Being Considered for Installation at a Municipal