A Carnot’s heat engine has an efficiency 1/6. When temperature of sink is reduced by 620C, its efficiency is doubled. Temperature of source and sink are,

efficiency of heat engine=η=1−T2T1        ;here temperature of source =T1;temperature of sink =T2⇒16=1−T2T1---(1)⇒T2T1=56---(2)new efficiency is η1=2η=26; when temperature of sink is reduced =T2−62η1=1−T2−62T1⇒26=1−T2T1+62T1   ; substitute eqn(1)⇒13=16+62T1⇒13-16=62T1⇒T1=62×6=372K⇒T1=372−273=990C;consider eqn(2)T2T1=56substitute T1=372,T2=56X372=310K⇒T2=310−273=370C