(i) When same work is done by both the engines,
Let’s assume that engine A takes heat Q1 from the source and gives heat Q2 to the sink, then
Carnot cycle
Now, lets assume engine Stakes heat Q2 from its source (at temperature T) and gives away Q3 to its sink (at temperature T = 400K). Then again from Carnot’s cycle.
(ii) When both engines have same efficiency.
Efficiency of engine A