#$10$: Let $D$ be the region between two concentric spheres $S_1$:$x^2+y^2+z^2=16$ and $S_2$:$x^2+y^2+z^2=49,$ i$.$e$.,$ the boundary of $D$ is delD$=S_1{S}_2.$ Let $F$ be a smooth vector field on $R^3$ such that grad$*F=x^2+y^2+z^2.$ Compute

${}_{\text{d}\text{e}\text{l}\text{D}}F*ndS,$

where $n$ is the orientation of the boundary surface chosen as the outward normal.

Hint: Use the Divergence Theorem.