Rotational Motion

A bullet, fired into a door gets embedded exactly at it's centre, causing the door to rotate about it's vertical axis, practically without friction, with an angular velocity of $0.625 \mathrm{rads}^{-1}$. The door is 1.0 m wide and weighs 12 kg . If the mass of the bullet is 10 g , find the speed with which it was fired. (Hint: The moment of inertia of the door about the vertical axis at one end is $\frac{M L^2}{3}$.