A desperate hiker has to think fast to help his friend who has fallen below him. Quickly, he ties a rope to a rock of mass m = 399 kg and makes his way over the ledge (see the figure). Assume the rope is parallel to the ground and the point where the rope passes over the ledge is frictionless. If the coefficient of static friction between the rock and the ground is us = 0.335, and the mass of the hiker is mr = mi = 74.9 kg, what is the maximum mass of the friend me that the rock can hold so the hikers can then make their way up over the ledge