A portion of the flue for a furnace is attached to the ceiling at A. While supporting the free end of the flue at F, a worker pushes in at E and pulls out at F to align end E with the furnace. Knowing that the 10-lb force at F lies in a plane parallel to the yz plane and that α = 60°, 

(a) Replace the given force system with an equivalent force-couple system at C, 

(b) Determine whether duct CD will tend to rotate clockwise or counterclockwise relative to elbow C, as viewed from D to C.