Question 6 (20 points): A motor with a 200-horsepower output is needed in a factory for intermittent use.A Graybar motor costs $7000 and has an electrical efficiency of 90%. A Blueball motor costs $6000 and has an 85% efficiency. Neither motor would have any salvage value, since the cost to remove it would equal its scrap value. The annual maintenance cost for either motor is estimated at $500 per year. Electric power costs $0.12/kWh (1 hp = 0.746 KW). If an 18% interest rate is used in the calculations, what is the minimum number of hours the higher initial cost Graybar motor must be used each year to justify its purchase? Assume a 20-year life for each motor.

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