Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of C.O.P. of reversed Carnot Cycle?

Answer: Option D

Efficiency of a Carnot engine is given as 80% or $$\eta$$ = 0.80
If the cycle direction be reversed
The relation between the effecicy and C.O.P. is defined by formula
$$\text{C}\text{.O}\text{.P}\text{.}=\frac{1-\eta }{\eta }=\frac{1-0.80}{0.80}=0.25$$