Answer
$F = 2.8\times 10^{-5}~N$
Work Step by Step
We can find the radiation force:
$F = \frac{2~I~A}{c}$
$F = \frac{2~P~A}{4\pi~r^2~c}$
$F = \frac{(2)~(3.90\times 10^{26}~W)~(2.0~m)^2}{(4\pi)~(3.0\times 10^{11}~m)^2~(3.0\times 10^8~m/s)}$
$F = 2.8\times 10^{-5}~N$
