The shaft in Figure P4.36 has a diameter of 20 mm and is made of a ductile steel (Y = 400 ma). It is subjected to a combination of static loads as follows: axial load P = 25.0 kN, bending moment M, = 50.0 N m, and torque T = 120 N m. FIGURE P4.36 a. Determine the factor of safety for a design based on the octahedral shear-stress criterion of failure. b. Determine the factor of safety for a design based on the maximum shear-stress criterion of