Two 180-horsepower (HP) motors are being considered for installation at a municipal sewage-treatment plant. The first cost $6,100 and has an operating efficient of 77%. The second cost $3,000 and has an efficiency of 72%. Both motors are projected to have zero salvage value after a life of 10 years. If all the annual charges, such as insurance, maintenance, ect., amount to a total of 19% 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=12%? (A conversion factor you might find useful is 1 HP= 746 watts= 0.746 kilowatts.)