Disk A, with a mass of 2.0 kg and a radius of 50. cm, rotates clockwise about a frictionless vertical axle at 30. rev/s. Disk B, 1.0 kg with a radius of 100. cm, rotates counterclockwise at 20. rev/s about the same axle, but at a greater height than disk A. Disk B slides down the axle until it lands on top of disk A, after which they rotate together. What is their common angular velocity in rev/s, and in which direction do they rotate?