A ladder, 8 m long and having a mass of 25 kg, rests on a horizontal floor and is supported by a vertical wall. The ladder is inclined 62°, as shown, and starts to slip when a person having a mass of 73 kg has climbed halfway up it. The coefficient of friction at the wall is 0.20. Assume the weight of the ladder to be concentrated at its midpoint. Calculate the coefficient of friction at the floor
