Answer
Please see the work below.
Work Step by Step
We know that
$P=\frac{F}{A}$
$\implies P=\frac{mg}{\pi r^2}$
This can be rearranged as
$m=\frac{\pi r^2P}{g}$
We plug in the known values to obtain:
$m=\frac{\pi (\frac{0.45}{2})^2(500,000)}{9.8}$
$m=8100Kg$
