Sir Dudley the Dextrous is loading cannons on top of the castle's tallest towers in preparation for an expected attack. He slips, and a cannonball of mass 6.00 kg rolls to the edge of the tower, which has a perfectly horizontal surface, and falls to the ground below. It takes the cannonball 1.65 s to fall to the ground, and air resistance is negligible. How much work is done by gravity on the falling cannonball?