$($a$)$ Knowing that $S_{\text{a}\text{I}\text{I}}=24$ksi and $t_{\text{a}\text{l}\text{l}}=14\mathrm{.}5$ksi select the most economical wideflange shape that should be used to support the loading shown. $($b$)$ Determine the values to be expected for $s_m,t_m$ and the principal stress $s_{\text{m}\text{a}\text{x}}$ at the junction of a flange and the web of the selected beam.