11-33 A plant manager has to choose between replacing five 4-hp standard motors and replacing one 20-hp standard motor with high-efficiency counterparts. The existing efficiency of the small motor is 0.83, and its replacement has an efficiency of 0.89. The efficiencies of the existing large motor and its replacement are 0.91 and 0.94, respectively. (a) Determine the annual electricity and cost savings for each replacement option. The motors operate 4500 hours a year, and the unit price of electricity is $0.105/kWh. (b) If the costs of the new small motor and the new large motor are $520 and $1250, respectively, determine the simple payback period of each replacement option.