Problem Four$-$ For the cross sections shown, Compute:

$($a$)$ the gross moment of inertia, $I_g$;

$($b$)$ the location of the neutral axis of the cracked section and the cracked moment of inertia $l_{cr}$

$($c$)I_e$ for $M_a=0\mathrm{.}55M_n$

The beams have a $1\mathrm{.}5in.$ of clear cover and No$.3$ stirrups.

The concrete strength is $4000$ psi; $f_y=60$ksi.

Blured lengt $=22"$