Surface Integrals, Stokes & Divergence · Medium problem

Let $S$ be the upper hemisphere $x^2 + y^2 + z^2 = 9$, $z \ge 0$ (the curved part only), with outward normal. Use the divergence theorem to find the flux of $\mathbf F = (x, y, z)$ through $S$. Give an exact answer in terms of $\pi$.