(a) find the maximum mass of a person who can walk to the extreme end d without tipping the beam. (hint: at that moment, the normal force on the beam due to wall a would be zero.) (b) find the forces that the walls a and b exert on the beam when the person is standing at d. (c) find the forces that the walls a and b exert on the beam when the person is standing at a point 2.0 m to the right of b. (d) find the forces that the walls a and b exert on the beam when the person is standing at a point 2.0 m to the right of a.