A disk, with a radius of 0.25 m, is to be rotated like a merry-go-round through 200 rad, starting from rest, gaining angular speed at the constant rate through the first 100 rad and then losing angular speed at the constant rate - until it is again at rest. The magnitude of the centripetal acceleration of any portion of the disk is not to exceed 100 m/s2. (a) What is the least time required for the rotation