$3.$ A cantilevered beam is subjected to a triangular distributed load of $\backslash ($ w$=12\backslash$mathrm$\{$kN$\}/\backslash$mathrm$\{$m$\}\backslash ).$ Using Mohr's Circle. Determine the principal stresses $(\backslash (\backslash$sigma$\_\{1\}\backslash )$ and $\backslash (\backslash$sigma$\_\{2\}\backslash ))$ at point $\backslash ($ A $\backslash ).$ Point $\backslash ($ A $\backslash )$ is located at a longitudinal distance of $5$ m to the right of the support and in the web cross section of the beam just above the lower flange. Present the appropriate FBD and a clearly defined coordinate system. Solutions without these elements will be graded as zero. Marks over the problem's image are not consider a proper FBD$.(20$ pts$)$