An engine has an efficiency of 1/3. When the temperature of sink is reduced by 56°C, its efficiency is halved. Temperature of the source is :

63°C

Since, efficiency of engine is : \(\eta = 1 - \frac{T_2}{T_1}\)

When the temperature of the sink is reduced by 56°C, its efficiency is doubled : \(\eta/2 = 1 - \frac{T_2 - 56}{T_1}\)

According to ques : \(\eta = \frac{1}{3}\)

⇒ T₂ = 336 K ; T₁ = 63°C = Temperature of source