A straight ladder is leaning against the wall of a house. The ladder has rails 3.20 m long, joined by rungs 0.530 m long. Its bottom end is on solid but sloping ground so that the top of the ladder is 0.670 m to the left of where it should be, and the ladder is unsafe to climb. You want to put a rock under one foot of the ladder to compensate for the slope of the ground.
(a) What should be the thickness of the rock?