By means of a rope whose mass is negligible, two blocks are suspended over a pulley, as the drawing shows, with m1 = 12.2 kg and m2 = 42.8 kg. The pulley can be treated as a uniform, solid, cylindrical disk. The downward acceleration of the 42.8-kg block is observed to be exactly one-half the acceleration due to gravity. Noting that the tension in the rope is not the same on each side of the pulley, find the mass of the pulley.