A cold-drawn steel shaft of 155 Bhn is 12 in. long, 1.25 in. in diameter, and has a 0.25-in.-diameter transverse hole. Surfaces have a machined finish. Estimate the safety factor with respect to infinite fatigue life for (a) a torque fluctuating between 0 and 60 lb.ft, (b) a completely reversed torque of 30 lb.ft, and (c) a mean torque of 35 lb.ft plus a superimposed alternating torque of 25 lb.ft.