3, In the figure, a rectangular beam is fixed at one end, and loaded by a distributed force w = 180 N/m acting on the half end of the beam. Draw the Mohr's circle for the stress elements of unit cubic located on the surface of the beam and is 1/4h from the top surface and 1/4L from the loading end. (b = 70 mm, h = 28 mm, L = 800 mm)