A uniform thin rod of mass \(M\) and length \(L\) is attached to a frictionless horizontal axle at one end. A small block of mass \(2M\) is fixed to the rod at a distance of \(\dfrac{3}{4}L\) from the axle. The system is held in a horizontal position and released from rest. At the instant of release, what is the magnitude of the angular acceleration of the rod-block system?