(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 50.0°C and a cold reservoir temperature of -20.0°C? 

(b) How much heat transfer occurs into the warm environment if 3.60 x 10⁷ J of work (10.0kW h) is put into it? 

(c) If the cost of this work input is 10.0 cents/kWh, how does its cost compare with the direct heat transfer achieved by burning natural gas at a cost of 85.0 cents per therm. (A therm is a common unit of energy for natural gas and equals 1.055 x 10⁸ J.)