4. (13 points) One end of a 13 meter rod is fixed on a wall, at a spot 20 meters above the floor. The rod is rotating counterclockwise at an angular velocity of 5 radians per minute. At the end of the rod, there is a laser whose beam ends on the floor as shown. The picture is not to scale. 13m 20m (a) How fast is the distance of the end of the rod from the floor, shown by h in the picture, decreasing when h = 15 meters? (b) How fast is the beam on the floor moving at that time