Heat is transferred from a geothermal vent to heat a greenhouse. The temperature inside the greenhouse must be 300 K at all times. If the outside temperature is lower than 300 K, heat is lost through the walls. To keep the greenhouse warm, a heat pump with a coefficient of performance equal to 1.8 has been constructed and requires 12 kW of power to operate. Assuming the outside temperature is 260 K, how much heat is lost through the walls per degree temperature difference?