Two 180-horsepower (HP) motors are being considered for installation at a municipal sewage-treatment plant. The first costs $5,800 and has an operating efficiency of 77%. The second costs $4,400 and has an efficiency of 74%. Both motors are projected to have zero salvage value after a life of 10 years. If all the annual charges, such as insurance maintenance, etc., amount to a total of 18% of the original cost of each motor, and if power costs are a flat five cents per kilowatt-hour, how many minimum hours of full-load operation per year are necessary to justify purchasing the more expensive motor at i=6% (A conversion factor you might find useful is 1 HPequals=746 wattsequals=0.746 kilowatts.)