Determine the shear stress and normal stress on infinitesimal elements D and E shown in a structural member below. Point D is at the top surface and point E is at the front surface. The structural member is fixed at the left end and subjected to a vertical load P1 and torque T1 at the right end. Draw elements D and E separately and clearly indicate the stresses acting on each isolated element. For each stress, clearly show its direction by arrows, and state the formula in terms of the internal force-resultants that you will use to calculate the stresses.