Question $3(25$ points$)$

Stress due to Bending of a Channel Beam

Beam $AB$ with a channel type cross section is subjected to two equal and opposite couples of magnitude $M=25kN*m$ as shown. The two couples are applied in such a way that the beam bends about the vertical $y-$axis such that point $C$ is in tension and point $D$ is in compression. Determine the normal stress in $[$MPa$]$ that develops at point $D$ due to this berding if the centroid coordinates for the beam cross$-$section is $x=44mm,y=90mm.$