Moment of inertia - parallel axis theorem

2026 Re-NEET 1 question

1. A solid sphere A of radius R and mass M is attached at a point to a smaller solid sphere B of radius r < R and mass m < M. Assume that the line joining their centres lies along the horizontal. The moment of inertia of the system calculated about a vertical axis passing through the centre of A is $I_A$ and that calculated about a vertical axis passing through the centre of B is $I_B$. The difference $I_A-I_B$ is: