6.(10 total points) Solve using integration. Consider the region \(\mathcal{R}\) in the \( x y \)-plane completely enclosed by the curves \( y=4 x-x^{2}\) and \( y=x \).(a)(5 points) Set up, but do not evaluate, an integral that computes the volume of the solid of revolution generated by revolving \(\mathcal{R}\) about the vertical line \( x=-1\).(b)(5 points) Set up, but do not evaluate, an integral that computes the volume of the solid of revolution generated by revolving \(\mathcal{R}\) about the horizontal line \( y=4\).