The efficiency of a heat pump is
$$\mathcal{\epsilon}_{ref}=\frac{T_C}{T_H-T_C}=\frac{275}{29}=9.48$$
where ##T_H=304K## is the hot reservoir and ##T_C=275K## is the cold reservoir.
The efficiency of the heat engine is
$$\mathcal{\epsilon}_{eng}=1-\frac{T_C}{T_H}=1-\frac{75}{304}=0.753$$...
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