Batman whose mass is 80 kg is dangling on the free end of a 12 m rope, the other end of which is fixed to a tree limb above. By repeatedly bending at the waist, he is able to get the rope in motion, eventually making it swing enough that he can reach a ledge when the rope makes a 60? angle with the vertical. How much work was done by the gravitational force on Batman in this maneuver.