Answer
$1.37*10^{-10}$
Work Step by Step
If we assume the area is spherical, then the area is proportional to the the radius squared. We can therefore find the ratio of intensities by using the ratio of the square of the distances.
We are given that $d=0.200*10^{-3}m$ and from part a, we know that $D=17.1m$.
The ratio of intensities is given by :
$(\frac{d}{D}^2)=(\frac{0.200*10^{-3}m}{17.1m}^2)=1.37*10^{-10}$
