(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 61.3\deg C and a cold reservoir temperature of -12.7\deg C? (b) How much heat in kilocalories would it pump into the warm environment if 3.60 107 J of work (10.0 kW . h) is put into it? kcal (c) Assume the cost of this work input is 10¢/kW h. Also assume that the cost of direct production of heat by burning natural gas is 87.0¢ per therm (a common unit of energy for natural gas), where a therm equals 1.055 108 J. Compare the cost of producing the same amount of heat by each method. cost of heat pump cost of natural gas =