$\eta_{1}=1-\frac{147+273}{447+273}=1-\frac{420}{720}$
$\eta_{1}=\frac{300}{720}$
$\eta_{2}=1-\frac{47+273}{947+273}=1-\frac{320}{1220}$
$\eta_{2}=\frac{900}{1220}$
$\frac{\eta_{1}}{\eta_{2}}=\frac{300}{720} \times \frac{1220}{900}=\frac{122}{72 \times 3}$
$\frac{\eta_{1}}{\eta_{2}}=0.56$
