Problem $3$: Forces $F_1=2000lbf$ and $F_2=3000lbf$ are exerted on the shaft which rotates at $1000re\frac{v}{m}in$ and made of $1050$ CD steel. The critical section of the shaft is at point $B.$ The surfaces are machined. $($a$)$ Find the reversible stress, ${}_{\text{r}\text{e}\text{v}},$ at the critical section. $($b$)$ Find the actual endurance limit$,S_e,$ for a $99\%$ reliability. $($c$)$ Estimate the fatigue factor of safety based on achieving infinite life and the yielding factor of safety. If infinite life is not predicted, estimate the number of cycles to failure.