$3\mathrm{.}7$ For Problems $3\mathrm{.}7$ to $3\mathrm{.}9$ determine the values of $lo{n}_1,$ and $M_n$ for the sections shown.

Problem $3\mathrm{.}7($Ans$.M_n=264\mathrm{.}1fl-k)$

Do psi

psi

Problems $3\mathrm{.}9($Ans$.$ Section has $lo{n}_t=0\mathrm{.}00368<mn>0</mn><mn>.</mn><mn>0</mn><mn>0</mn><mn>4</mn>$ Therefore it may not be used.$)$