Two steels are being considered for manufacture of as$-$forged connecting rods subjected to bending loads. One is AISI $4340$ Cr$-$Mo$-$Ni steel capable of being heat$-$treated to a tensile strength of $260$ kpsi. The other is a plain carbon steel AISI $1040$ with an attainable Sut of $113$ kpsi. Each rod is to have a size giving an equivalent diameter de of $0\mathrm{.}75$ in$.$ Determine the endurance limit for each material. Is there any advantage to using the alloy steel for this fatigue application? What is the value for k$\_$d$,$ k$\_$e$,$ and k$\_$f$?$