A professor's office door is 0.99 m wide, 2.2 m high, 4.2 cm thick; has a mass of 27 kg, and pivots on frictionless hinges. A "door closer" is attached to door and the top of the door frame. When the door is open and at rest, the door closer exerts a torque of 5.6 N*m. What is the moment of inertia of the door? If you let go of the open door, what is its angular acceleration immediately afterward?