10. (10 points) Let $F(x,y,z)=\dfrac{x\mathbf{i}+y\mathbf{j}+z\mathbf{k}}{(x^2+y^2+z^2)^{3/2}}$ and let $D=\left\{(x,y,z)\mid \dfrac{x^2}{4}+\dfrac{y^2}{4}+\dfrac{z^2}{9}=1\right\}$. Find the flux of $F$ outward across the boundary of $D$.