An extruded polymer flexural member is subjected to an internal axial force of P = 580 lb, an internal shear force of V = 420 lb, and an internal bending moment of M = 6,400 lb·in., acting in the directions shown in Figure P12.5a. The cross-sectional dimensions (Figure P12.5b) of the extrusion are b1 = 2.0 in., t1 = 0.6 in., b 2 = 4.0 in., t2 = 0.4 in., d = 4.5 in., and tw = 0.4 in. Determine the normal and shear stresses acting on horizontal and vertical planes: (a) at point H, which is located at a distance of yH = 0.8 in. above the z centroidal axis. (b) at point K, which is located at a distance of yK = 1.1 in. below the z centroidal axis. Show the stresses on a stress element for each point