A three-step cycle is undergone by n moles of an ideal diatomic gas: (1) the temperature of the gas is increased from T_1 to T_2 at constant volume; (2) the gas is then isothermally expanded to its original pressure; (3) the gas is then contracted at constant pressure back to its original volume. Throughout the cycle, the molecules rotate but do not oscillate. What is the efficiency of the cycle in terms of T_1 and T_2?