Surface Integrals, Stokes & Divergence · Medium problem

Let $E$ be the spherical shell $1 \le x^2 + y^2 + z^2 \le 4$. Use the divergence theorem to find the outward flux of $\mathbf F = (2x - y^2,\ z + x,\ 3z)$ through the boundary of $E$ (both spheres, each with normal pointing out of $E$). Give an exact answer in terms of $\pi$.