$4\mathrm{.}41$: The $612-$in$.$ timber beam has been strengthened by bolting to it the steel reinforcement shown. The modulus of elasticity for wood is $1\mathrm{.}81^{6\text{a}\text{n}\text{d}\text{f}\text{o}\text{r}\text{s}\text{t}\text{e}\text{e}\text{l}is}29{10}^6$psi. Knowing that the beam is bent about a horizontal axis by a couple of moment $M=450$kip$-$in$.,$ determine the maximum stress in $($a$)$ the wood, $($b$)$ the steel.