Question

An engine using 1 mol of an ideal gas ini- tially at 21.7 L and 326 K performs a cycle consisting of four steps:
1) an isothermal expansion at 326 K from 21.7 L to 42.1 L;
2) cooling at constant volume to 186 K ;
3) an isothermal compression to its original volume of 21.7 L; and
4) heating at constant volume to its original
temperature of 326 K .
Find its efficiency. Assume that the
heat capacity is 21 J/K and the univer- sal gas constant is 0.08206 L · atm/mol/K = 8.314 J/mol/K.
Answer in units of %.