The efficiency of a heat engine that works between the temperatures where Celsius-Fahrenheit scales coincides and Kelvin-Fahrenheit scales coincides is (approximately)

Step-by-step solution

When Celsius - Fahrenheit scale coincide, aligned & F -32 180 = C -0 100 ~T ₁-32 9 = C 5 & ~T ₁=-40^ C aligned When kelvin - Fahrenheit scale coincide, aligned & K -273 100 = F -32 180 ~T ₂-273 5 = T ₂-32 9 & ~T ₂=574.25 ~K & Efficiency, =1- T ₁ ~T ₂ =1- 273-40 574.25 =60 % aligned