A reversible heat engine converts one – fourth of the heat input into work. When  the temperature of the sink is reduced by 52K, its efficiency is doubled. The  temperature in Kelvin of the source will be ——

η=1-T2T1Case 1 : If heat engine converts one – fourth of the heat input into workthen its efficiency =1414=1-T2T1⇒34=T2T1⇒T2=34T1Case 2 : If the temperature of the sink is reduced by 52K, its efficiency is doubled24=1-T2-52T1⇒T2-52T1=12⇒T2-52=T12⇒34T1-52=T12  ⇒T1=208 K