Two electric motors are available to satisfy a continuous demand of 85 kW. Motor 1 has an initial cost of $5,500 with an operating efficiency of 91%. Motor 2 has an initial cost of $4,000 with an operating efficiency of 89%. Each motor has a life of 10 years with no salvage value. The annual cost of electricity to run the machines is $19.20 per kW of demand plus $0.12 per kWh of energy use. Determine the number of runtime hours that makes these two motors economically equivalent to each other if the MARR is 22%.