A 5m long ladder, weighs 200N, rests against a smooth vertical wall with its base on a horizontal rough floor,a distance of 1.3 m away from the wall. The center of mass of the ladder is 2.5 m from its base, and the coefficient of static friction between the ladder and the floor is 0.2. How far up the ladder, measured along the ladder, can a 600N person climb before the ladder begins to slip?