Answer
(a) $6.10\%$
Work Step by Step
We can find the required maximum efficiency as follows:
$e_{max}=1-\frac{T_c}{T_h}$
We plug in the known values to obtain:
$e_{max}=1-\frac{273+4}{273+22}$
$e_{max}=1-\frac{277}{295}$
$e_{max}=0.0610$
$e_{max}=6.10\%$
