A certain area can be irrigated by piping water from a nearby river. Two competing installations are being considered, for which the following engineering and cost data apply :

6-inch System 8-inch System

Size motor required       25 hp        10 hp

Energy cost per hour of operation $ 1.25 $ 0.55

Cost of motor installed $ 800 $ 500

Cost of pipe and fittings $ 2,900 $ 3,700

Salvage value at end of 10 years $ 360 $ 280

On the basis of a 10-year life with an interest rate of 12%, determine the number of hours of operation per year for which the two systems will break even.