$4-2$ A cantilever beam shown in Fig. P$4-2$ supports a

uniform dead load of $1ki\frac{p}{f}t$ plus its own weight

and a concentrated live load of $12$ kips $,$ as shown.

The concrete is normal$-$weight concrete with $f_c^{\text{'}}=$

$4000$ psi $,$ and the steel is Grade $60.$ For the section

at the fixed support, shown in Fig. P$4-2$b$,$ compute

$M_n$ and show that it exceeds $M_u.$

$($a$)$

$6$ No$.8$ bars

$($b$)$

Fig. P$4-2$