A solid disk of mass 1.45 kg and radius 25.0 cm is initially spinning counterclockwise (as viewed from above) at 15.5 revolutions per second on a massless and frictionless bearing. A second disk, of mass 1.05 kg and radius 12.5 cm is initially spinning clockwise about the same axis at 14.2 revolutions per second, is dropped on top of the first disk. Because there is friction between the disks, they quickly reach a common angular speed. What is their final angular speed, in revolutions per second