A Carnot cycle is having an efficiency of $$0.75.$$ If the temperature of the high temperature reservoir is $${727^ \circ }C,$$ what is the temperature of low temperature reservoir?

A cyclic heat engine does $$50$$ $$kJ$$ of work per cycle. If the efficiency of the heat engine is $$75\% $$, then heat rejected per cycle is

For two cycles coupled in series, the topping cycle has an efficiency of $$30\% $$ and the bottoming cycle has an efficiency of $$20\% $$. The overall combined cycle efficiency is

A solar energy based heat engine which receives $$80$$ $$kJ$$ of heat at $${100^ \circ }C$$ and rejects $$70$$ $$kJ$$ of heat to the ambient at $${30^ \circ }C$$ is to be designed. The thermal efficiency of the heat engine is