A Kansas farmer heats his house with a heat pump using R134a, generating a temperature of 50 deg C at the exit of the (isentropic) compressor. The evaporator is buried at a depth of 2 meters and has a temperature of 15 degrees C. The evaporator exit, which is the compressor entrance, is saturated vapor. Assume that the condenser exit is liquid, whose temperature is 7 degrees below saturated liquid. Assume a throttling valve is downstream of the condenser. Determine the coefficient of performance.