A desperate hiker has to think fast to help his friend who has fallen below him. Quickly, he ties a rope to a rock m_r= 402 kg and makes his way over the ledge (see figure). If the coefficient of static friction between the rock and ground is μ_s= 0.322, and the mass of the hiker is μ_h=74.9 kg, what is the maximum mass of the friend, m_f,that the rock can hold so the hikers can then make their way up over the ledge? Assume the rope is parallel to the ground and the point where the rope passes over the ledge is frictionless.

 

m Number kg