The question is:$16.$ A solid wooden door has a moment of inertia about its hinged side of $.$ It is open and at rest. A small ball is thrown perpendicular to the door with a speed of and hits the door from the hinged side, causing it to begin turning. The ball rebounds along the same line with a speed of relative to the ground.$($a$)$ What is the magnitude of the change in angular momentum of the ball because of the collision with the door about the axis of the door hinges?$($b$)$ What is the magnitude of the final angular velocity of the door right after the collision? $($If you did not get part a$,$ just assume the answer to part a is $).$