(Solved): The frustum is formed by rotating the shaded area around the x axis. The frustum has a constant den ...

The frustum is formed by rotating the shaded area around the $x$ axis. The frustum has a constant density $?$ and the total mass $m$. (Figure 1) Determine the moment of inertia $I_x$ and express the result in terms of the total mass $m$ of the frustum. Express your answer in terms of some or all of the variables $m,a$, and $b$.