Final answer:
The highest coefficient of performance that a heat pump operating between two reservoirs can have is 1.33.
Step-by-step explanation:
The best coefficient of performance possible for a heat pump operating between two reservoirs can be calculated using the Carnot efficiency. The Carnot efficiency is given by the equation Effc = 1 - (Tc/Th), where Tc is the temperature of the cold reservoir and Th is the temperature of the hot reservoir. To find the highest coefficient of performance, we want the lowest possible temperature for the cold reservoir. In this case, the cold reservoir temperature is -15.0°C. Using the Carnot efficiency equation, we can calculate the highest coefficient of performance as Effc = 1 - (-15.0°C/45.0°C) = 1 - (-1/3) = 4/3 or 1.33.