Answer:
35.2 %
Explanation:
The maximum possible theoretical efficiency of an engine is given by:
[tex]\eta=1-\frac{T_C}{T_H}[/tex]
where
[tex]T_C[/tex] is the low-temperature reservoir
[tex]T_H[/tex] is the hot-temperature reservoir
For the engine in this problem, we have
[tex]T_C = 350 K\\T_H=540 K[/tex]
Substituting into the equation, we find
[tex]\eta=1-\frac{350 K}{540 K}=0.352=35.2 \%[/tex]