The performance of a heat pump degrades (ie., its COP decreases) as the temperature of the heat source decreases. This makes using heat pumps at locations with 5evene weather conditions

unattractive. Consider a house that is heated and maintained at 20 C by a heat pump during the winter. What is the maximum COP for this heat pump it heat is extracted from the outdoor air at (a) 10"C, (b) -5"C, and (-30 C?