$3.(6$ marks$)$ Answer the following problems.

a$)$ Determine the plastic moment capacity $\backslash ($ M$\_\{\backslash$mathrm$\{$p$\}\}\backslash )$ of the following I$-$beam section. Take yield stress as $265$ MPa $.$

$(2$ marks$)$

b$)$ Use the upper bound theorem and the plastic moment capacity $\backslash ($ M$\_\{$p$\}\backslash )$ in previous part to estimate the collapse load $\backslash ($ P $\backslash )$ of the following continuous beam.

$(4$ marks$)$

Fig. $1-3$ Two$-$span continuous steel beam