A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 620C, the efficiency of the engine is doubled. The temperatures of the source and sink are

Initially η = (1-T2T1) = WQ = 16--------------(i)Finally η' = (1-T2'T1) = (1-(T2-62)T1)                   = 1-T2T1+62T1                      = η+62T1---------------(ii)It is given that η' = 2η. Hence solving equations (i) and (ii)⇒ T1 = 372 K = 990C and T2 = 310 K = 370C