A short bar magnet having magnetic moment \(4 \mathrm{Am}^2\), placed in a vibrating magnetometer, vibrates with a time period of \(8 \mathrm{~s}\). Another short bar magnet having a magnetic moment \(8 \mathrm{Am}^2\) vibrates with a time period of \(6 \mathrm{~s}\). If the moment of inertia of the second magnet is \(9 \times 10^{-2} \mathrm{~kg}-\mathrm{m}^2\), the moment of inertia of the first magnet is (assume that both magnets are kept in the same uniform magnetic induction field.)

1. A \(9 \times 10^{-2} \mathrm{~kg}-\mathrm{m}^2\)
2. B \(8 \times 10^{-2} \mathrm{~kg}-\mathrm{m}^2\)
3. C \(5.33 \times 10^{-2} \mathrm{~kg}-\mathrm{m}^2\)
4. D \(12.2 \times 10^{-2} \mathrm{~kg}-\mathrm{m}^2\)