Suppose that the rod is held at rest horizontally and then released. (Throughout the remainder of this problem, your answer may include the symbol I, the moment of inertia of the assembly, whether or not you have answered the first part correctly.) What is the angular acceleration α of the rod immediately after it is released? Take the counterclockwise direction to be positive. Express α in terms of some or all of the variables mr, m1, m2, x, I, and g.