A cylinder fitted with a piston contains 0.5 kg of R-134a at 60?C, with a quality of 50%. The R-134a now expands in an internally reversible polytropic process to ambient temperature, 20?C, at which point the quality is 100%. Any heat transfer is with a constant-temperature source, which is at 60?C. Find the polytropic exponent n and show that this process satisfies the entropy equation.