For a Carnot engine T1 > T2. When T2 is decreased by $\triangle T$ with T1 remaining same then efficiency
is $\eta _{1}$, and when T1 s increased by $\triangle T$ with T2 remaining same efficiency is $\eta _{2}$ Which one of the following is the correct expression for ( $\eta _{1}-\eta _{2}$) ?
