Answer
Please see the work below.
Work Step by Step
We know that the radiation rate is given as
$P=\sigma AT^4$
This can be rearranged as:
$A=\frac{P}{\sigma T^4}$
We plug in the known values to obtain:
$A=\frac{100}{(5.7\times 10^{-8})(3000)^4}$
$A=2.2\times 10^{-5}m$
