The steam, initially at a pressure of 15 bar and a temperature of \(250^{\circ} \mathrm{C}\), expand reversibly and polytropically to \(1.5 \mathrm{bar}\). Find the final temperature, work done, and change of entropy, if the index of expansion is 1.25. (Assume 1 bar \(=1.013 \times 10^{2} \mathrm{kPa}\) ). State the assumptions made.