A 10-ft steel beam is lowered by means of two cables A & B distant of 9-ft, unwinding at the same speed from overhead cranes. As the beam approaches the ground, the crane operators apply brakes to slow down the unwinding motion. At the instant considered the deceleration of the cable attached at A is 12-ft/s^2, while that of cable B is 5-ft/s^2. Determine (a) the angular acceleration of the beam, (b) the acceleration of point C, when B & C are distant of 1-ft and A & C of 10-ft.