The merry-go-round at an amusement park is made up of a vertical center shaft with a number of horizontal arms attached to it at the top. The top end of a 7.00 m long cable is attached to an arm, 4.00 m from the central shaft and suspends a seat from the lower end. If the cable holding a seat makes a 60.0° angle with the vertical, find the duration of one swing revolution.