Two identical 10-kg spheres are attached to the light rigid…

Two identical 10-kg spheres are attached to the light rigid rod, which rotates in the horizontal plane centered at O. If the spheres are subjected to tangential forces of 10 N, and the rod is subjected to a couple moment M = (8t) N·m, where t is in seconds, select the best answer for the speed of the spheres at the instant t = 4 s. The system starts from rest. Neglect the size of the spheres.