Answer
See the detailed answer below.
Work Step by Step
a) Find the maximum temperature in Celsius of an engine that has a maximum efficiency of 0.8 and its minimum temperature is 0$^\circ$C.
b) Solving for $T_H$;
$$\dfrac{0+273}{T_H+273}=1-0.8$$
$$T_H=\dfrac{0+273}{1-0.8}-273= \color{red}{\bf 1092}^\circ\;\rm C $$
