$3.\backslash ([\backslash$mathbf$\{10\}\backslash$mathbf$\{$~ p t s$\}]\backslash )$ A thin$-$walled beam with a cross$-$section shown is subjected to a shear force, $\backslash (\backslash$mathrm$\{$V$\}=30\backslash$mathrm$\{$kN$\}\backslash ),$ and a bending moment, $\backslash (\backslash$mathrm$\{$M$\}=2\backslash$mathrm$\{$kN$\}-\backslash$mathrm$\{$m$\}\backslash )($not shown$).($a$)$ Calculate the maximum shear flow in the beam, $($b$)$ sketch the shear stress distribution over the entire cross$-$section and show the shear flow direction in each section, and $($c$)$ calculate the maximum normal stress in the beam.