Answer
(a) $0.896$
(b) $0.701$
Work Step by Step
(a) We can find the efficiency of the engine as follows:
$e=\frac{W}{Q_h}$
We plug in the known values to obtain:
$e=\frac{1120J}{1250J}$
$e=0.896$
(b) We can find the required efficiency as
$e=1-\frac{T_c}{T_h}$
We plug in the known values to obtain:
$e=1-\frac{302K}{1010K}$
$e=0.701$
