The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are

• (COP)R = (COP)HP = 0.6
• (COP)R = 2.5; (COP)HP = 1.5
• (COP)R = 1.5; (COP)HP = 2.5
• (COP)R = (COP)HP = 2.5