Use Green's Theorem to evaluate the line integral of $\mathbf{F} = \left< x^{3}, 3 x\right>$

around the boundary of the parallelogram in the following figure (note the orientation).

With $x_0=6$ and $y_0=6$.

$\int_{\mathcal{C}} x^{3} \,dx+3 x \,dy =$