Surface Integrals, Stokes & Divergence · Easy problem

Let $E$ be the solid tetrahedron $x \ge 0$, $y \ge 0$, $z \ge 0$, $x + y + z \le 3$. Use the divergence theorem to find the outward flux of $\mathbf F = (x,\ 2y,\ 3z)$ through the boundary of $E$.