question_answer

Two Carnot engines A and B are operated in series. Engine A receives heat from a reservoir at \[600K\] and rejects heat to a reservoir heat to reservoir at temperature\[T\]. Engine\[B\] receives heat rejected by engine \[A\] and in turn rejects it to a reservoir at\[100K\]. If the efficiencies of the two engines A and B are represented by \[{{\eta }_{A}}\] and \[{{\eta }_{B}}\] respectively, then what is the value of \[\frac{{{\eta }_{A}}}{{{\eta }_{B}}}\] [JEE Online 15-04-2018 (II)]

A)  \[\frac{12}{7}\]            

B)       \[\frac{12}{5}\]

C)  \[\frac{5}{12}\]            

D)       \[\frac{7}{12}\]