Answer:
35.2 %
Step-by-step explanation:
The maximum possible theoretical efficiency of an engine is given by:
![\eta=1-(T_C)/(T_H)](https://img.qammunity.org/2020/formulas/physics/middle-school/j8sfzmwb94wsw6h2s382gai7t8y8nc1m7f.png)
where
is the low-temperature reservoir
is the hot-temperature reservoir
For the engine in this problem, we have
![T_C = 350 K\\T_H=540 K](https://img.qammunity.org/2020/formulas/physics/middle-school/rg7uowo20dawexweh5d1bqadt1ve5d5n1y.png)
Substituting into the equation, we find
![\eta=1-(350 K)/(540 K)=0.352=35.2 \%](https://img.qammunity.org/2020/formulas/physics/middle-school/vnk8cmixu294sdfgf6kvrsqmcwrb6hk0ek.png)