A family is considering replacing their hot water heater. A conventional electric hot water heater is $200 including instalation. his brother and his wife now move in and they estimate that a family of four uses an average of 300 liters of hot water a day, which will require $350 worth of electricity each year. The installed cost of small solar water heater system is $1,400 and will cost $60 per year on the average to operate(electricity to pump the water through the panels and to augment solar heating on cloudy days. Both systems will have a $0 salvage value at the end of their useful lives. Based on a MARR of 12%, determine how long the soalr system must operate to make it as economical as the electric system.