$3\mathrm{.}17$ A rectangular section with $b=14$ in $.$ and effec$-$

tive depth $d=21\mathrm{.}5in.$ has $4$#$10$ as tension

reinforcement and $2-$#$10$ as compression rein$-$

forcement centered $2\mathrm{.}5$ in $.$ from the face of the

beam. Determine the strength $M_n$ for this sec$-$

tion. How much can the strength be increased

by adding tension steel only when the case is

governed by ACI$-9\mathrm{.}3\mathrm{.}3\mathrm{.}1?$ At the point where

compression steel is needed to further increase

strength by adding tension steel, what ratio

of $A_s^{\text{'}}$ to $A_s$ would require to be added? Use

$f_c^{\text{'}}=5000$ and ;

$d=546mm$; tension steel, $4$ #$32$M; compress$-$

ion steel, $2-$#$32M$ centered $63\mathrm{.}5$ mm from face;

$($:$f_c^{\text{'}}=35$MPa;$f_y=400$MPa$\}$