Answer
$56$
Work Step by Step
We can find the ratio of net power as
$\frac{P_1}{P_2}=\frac{e\sigma A(T_1^4-T_s^4)}{e\sigma (T_2^4-T_s^4)}$
We plug in the known values to obtain:
$\frac{P_1}{P_2}=\frac{(273.15+98)^4+(273.15+21)^4}{(273.15+23)^4-(273.15+21)^4}=56$
