Finally $\eta ' = \left( {1 - \frac{{{T_2}'}}{{{T_1}}}} \right) = \left( {1 - \frac{{({T_2} - 62)}}{{{T_1}}}} \right) = 1 - \frac{{{T_2}}}{{{T_1}}} + \frac{{62}}{{{T_1}}}$
$ = \eta + \frac{{62}}{{{T_1}}}$ ....$(ii)$
It is given that $\eta ' = 2\eta .$ Hence solving equation $ (i)$ and$(ii)$
==> ${T_1} = 372\,K = 99^\circ C$ and ${T_2} = 310K = 37^\circ C$



Reason $R$ : The efficiency of Carnot's engine depends not only on temperature of cold reservoir but it depends on the temperature of hot reservoir too and is given as $\eta=\left(1-\frac{ T _2}{ T _1}\right)$.
In the light of the above statements, choose the correct answer from the options given below

