A Carnot engine is working between \[127{}^\circ C\] and \[27{}^\circ C.~\]The increase in efficiency will be maximum when the temperature of

• A. the source is increased by \[50{}^\circ C\]
• B. the sink is decreased by\[50{}^\circ C\]
• C. source is increased by \[25{}^\circ C\]and that of sink is decreased by \[25{}^\circ C\]
• D. both source and sink are decreased by \[25{}^\circ C\]