Many modern houses use heat pumps for winter heating and then their owners reverse the cycle and enjoy summer cooling from the same machine. In a particular design, the interior temperature is desired to be 20°C in the winter and 25°C in the summer. Heat transfer through the walls and the ceilings is estimated to be 2400 kJ per hour per degree temperature difference between the inside and the outside. a) If the winter outside temperature is 0°C, what is the minimum power required to drive the heat pump (kW)? b) For the same power as in part a), what is the maximum outside temperature (°C) for which the house can be maintained at 25°C?