How to calculate the Moment of Inertia of a sphere with a spherical cavity. Easy to make a mistake!

We subtract the Moment of Inertia of a small sphere from that of a big sphere, taking care to use the correct masses and radii in the formula for the Moment of Inertia of a solid sphere. We will need to use the Parallel Axis Theorem to find the Moment of Inertia of the small sphere about the axis shown. The answer should be given in terms of the mass of the Sphere with the Cavity.