3. Use the Stokes' theorem to evaluate the line integral $\oint \mathbf{F} \cdot \mathbf{d r} $, where $C$ is oriented count-clockwise as viewed from above, $$ \mathbf{F}=x y \mathbf{i}+y z \mathbf{j}+2 x \mathbf{k} $$ and $C$ is the boundary of the part of the paraboloid $z=1-x^{2}-y^{2}$ in the first octant. CS.VS. 1595|