A magnetic needle of magnetic moment $6.7 \times 10^{-2}Am^2$ and moment of inertia $7.5 \times 10^{-6}\;kg \;m^2$ is performing simple harmonic oscillations in a magnetic field of $0.01\; T$. Time taken for 10 complete oscillations is :

Question

$\begin{array}{1 1}(1) 6.65 s \\ (2) 8.89 s \\ (3) 6.98 s \\ (4) 8.76 s \end{array} $