A possible ideal-gas cycle operates as follows: (i) from an initial state (p1, V1) the gas is cooled at constant pressure to (p1, V2); (ii) the gas is heated at constant volume to (p2, V2); (iii) the gas expands adiabatically back to (p_1, V_1). Assuming constant heat capacities, show that the thermal efficiency is 1 - gamma (V_1/V_2) - 1/(p_2/p_1) - 1 (You may quote the fact that in an adiabatic change of an ideal gas, pV^gamma stays constant, where gamma = c_p/c_v.)