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$5\mathrm{.}6$ A rectangular beam section is $b=16$ in$.$ wide and has a structural effective depth of $d=26\mathrm{.}5$ in$.$ Flexural reinforcement consists of three No$.9$ bottom bars and two #$9$ top bars. The beam is simply supported $($subjected to positive moment so the top of the beam is in compression and the bottom of the beam is in tension$).$ Given that the factored shear $\text{'}Vu\text{'}$ on the section is $90$kips, and a specified concrete strength of $4000,$ determine the required spacing of No$.4$ stirrups. Reinforcing bars are all fy$=60,000$psi.

$b$:$=16in,d=26\mathrm{.}5in,$:$=1\mathrm{.}0,f_c^{\text{'}}$:$=4000,f_{yt}$:$=60000$

$A_2$:$=2*0\mathrm{.}20i{n}^2=0\mathrm{.}40i{n}^2,$:$=0\mathrm{.}75$