Answer
(a) $585MW$
(b) $0.3019$
Work Step by Step
(a) We know that
$Heat \space provided=Work \space done+Heat \space discarded$
This can be rearranged as:
$Heat \space discarded=Heat \space provided-Work \space done$
$Heat\space discarded=838-253=585MW$
(b) As $\eta=\frac{Work\space done}{Heat \space input}$
We plug in the known values to obtain:
$\eta=\frac{253}{838}$
$\eta=0.3019$
