Two bar magnets \(A\) and \(B\) are placed one over the other and are allowed to vibrate in a vibration magnetometer. They make 20 oscillations per minute when the similar poles of \(A\) and \(B\) are on the same side, while they make 15 oscillations per minute when their opposite poles lie on the same side. If \(M_A\) and \(M_B\) are the magnetic moments of \(A\) and \(B\) and if \(M_A>M_B\), the ratio of \(M_A\) and \(M_B\) is

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.