Answer
Please see the work below.
Work Step by Step
We know that
$KE=\frac{1}{2}mv^2$
This can be rearranged as:
$m=\frac{2KE}{v^2}$
We plug in the known values to obtain:
$m=\frac{2\times 500\times 4.18\times 10^{12}}{19\times 10^3}=11.58\times 10^6Kg$
