An ideal gas heat engine operates in a Carnot Cycle between temperatures of 266 and 115°C. It absorbs 4250 cal per cycle at 266°C. What is its efficiency as a percentage?

Answer 1

Thot = 266 + 273 = 539
Tcold = 115 + 273 = 388

That is all you need for Carnot efficiency

eff = 100 (1 - Tc/Th) = 100(1-388/539)
=28 percent