#### Answer

Please see the work below.

#### Work Step by Step

(a) We know that
$e=\frac{W}{Q_h}$
We plug in the known values to obtain:
$e=\frac{350}{900}$
$e=0.39$
(b) We know that
$Q_c=Q_h-W$
We plug in the known values to obtain:
$Q_c=900-350$
$Q_c=550J$
(c) As $\frac{T_h}{T_c}=\frac{Q_h}{Q_c}$
We plug in the known values to obtain:
$\frac{T_h}{273+10}=\frac{900}{550}$
$T_h=460K$