A three-step cycle is undergone by n moles of an ideal diatomic gas: (1) the temperature of the gas is increased from T1 to T2 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 T1 and T2?