(a) What is the best coefcient of performance for a heat pump that has a hot reservoir temperature of 600C and a cold reservoir temperature of -20.0C? 4,1625 (b) How much heat transfer (in kcal) occurs into the warm environment if 3.60 x 107 J of work (10.0 kW - h) is put into it? 8.59 ' x kcal (c) If the cost of this work input is 10/kw ~ h, how does its cost compare with the direct heat transfer achieved by burning natural gas at a cost of 87.0 cents per therm. (A therm is a common unit of energy for natural gas and equals 1.055 x 103 J.) cost of heat pump = fl X cost of natural gas 7