You place a magnetic compass on a horizontal surface, allow the needle to settle into its equilibrium position, and then give the compass a gentle wiggle to cause the needle to oscillate about that equilibrium position. The frequency of oscillation is 0.370 Hz. Earth's magnetic field at the location of the compass has a horizontal component of 16.0 ?T. The needle has a magnetic moment of 0.700 mJ/T. What is the needle's rotational inertia about its (vertical) axis of rotation?