Answer
$I = 83~W/m^2$
Work Step by Step
We can find he radius of the laser's area at a distance of $40~m$:
$r = (\frac{0.17\times 10^{-3}~rad}{2})(40~m) = 3.4\times 10^{-3}~m$
We can find the intensity at a distance of $40~m$:
$I = \frac{P}{A}$
$I = \frac{P}{\pi~r^2}$
$I = \frac{3.0\times 10^{-3}~W}{(\pi)~(3.4\times 10^{-3}~m)^2}$
$I = 83~W/m^2$
