We saw in Chapter 4 that the heat capacity of nonmetallic solids at sufficiently low temperatures is proportional to T3, as C = aT3.Assume it were possible to cool a piece of such a solid to T = 0 by means of a reversible refrigerator that uses the solid specimen as its (varying!) low-temperature reservoir, and for which the high-temperature reservoir has a fixed temperature Th equal to the initial temperature Ti of the solid. Find an expression for the electrical energy required.