Answer
$2.5\times10^{25}W$.
Work Step by Step
At a distance r from the star, the total average power from the star is spread over a spherical surface, of area $4 \pi r^2$.
$$P_{av}=I4\pi r^2$$
$$=(5.0\times10^3W/m^2)(4 \pi)(2.0\times10^{10}m)^2=2.5\times10^{25}W $$