3. (a) A structural member, which is a made from a material with a uniaxial stress of Y = 400 MPa, is subjected to a state of plane stress. The stresses at a critical point in the member when the design loads are applied are given by: σx = 90 MPa, σy = −55 MPa and τxy = 40 MPa. If the structural member fails by plastic yielding when the design loads are applied, what safety factor was used in the design? Assume von Mises yield criterion.