A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62oC, the efficiency of the engine is doubled. The temperatures of the source and sink are

Efficiency of the engine η=Work/Qinput
As W=1/6Qinput ⇒ η=1/6
Also η=1−T2/T1 where T1 and T2 are the temperatures of source and sink respectively
∴1/6=1−T2/T1 ⇒T1=1.2T2 (1)
Now the sink temperature is reduced by 62oC, i.e T′2=T2−62
Also the new efficiency η′=2×1/6=2/6
η′=1−T′2/T1
2/6=1−(T2−62)/1.2T2 ⇒T2=310K
Thus T2=310−273=37oC
From (1), T1=1.2×310=372K ∴T1=372−273=99oC