You need to use tables to solve the question according to the mechanical design book

Q4: The figure bellow shows a shaft and the fluctuating nominal stress acting on it. The shaft is made of AISI 1095 Hot-Rolled steel. The fatigue stress concentration factors at the critical sections A,B, and C are given as: Section A: Bending Kf=2.0, Torsional Kf=1.75 Section B: Bending Kf=1.5, Torsional Kf=1.35 Section C: Bending Kf=1.7, Torsional Kf=1.40 Estimate the factor of safety guarding against fatigue failure if the nominal stresses are combined (bending plus torsional) of the same magnitude and phase as shown