An ideal Carnot heat engine operates on a temperature difference of $210$ degrees. One third of the heat absorbed from the source is discharged to the sink. If the work done per cycle is $400\; J$. Efficiency $(\eta)$ of an ideal carnot heat engine is

Question

$(a)\;0.52 \\(b)\;0.86 \\(c)\;0.66 \\(d)\;0.77 $