For the beam shown in Fig. $4($a$),$ calculate the maximum compressive and tensile stresses produced for the CO$4[20]$ section shown in Fig, $4($b$).$

$[$Marks distributions: $SFD,BMD=5,$ Moment of inertia $=5,$ stress calculation $=5,$ flexural stress diagram $=5]$

$($a$)$

$($b$)$

Fig. $4.$ for Question $4($dimensions are in $mm)$