A cold drawn steel rod of circular cross-section is subjected to a variable bending moment of 565 N- m to 1130 N-m as the axial load varies from 4500 N to 13 500 N. The maximum bending moment occurs at the same instant that the axial load is maximum. Determine the required diameter of the rod for a factor of safety 2. Neglect any stress concentration and column effect. Assume the following values: Ultimate strength Yield strength Size factor Surface finish factor Correction factors 550 MPa - 470 MPa - 0.85 -0.89 1.0 for bending 0.7 for axial load The endurance limit in reversed bending may be taken as one-half the ultimate strength.