For a three$-$span continuous beam, with deflection limited to L$/360$ of the span length, the minimum required cross$-$section area $($A$)$ of a joist section is in ${?}^2.($Reference equation:

$($:$F_v^{\text{'}}=\frac{0\mathrm{.}9wl}{bd}\}$

Assume:

Total form vertical design load $(q)=150l\frac{b}{f}{t}^2$

Spacing of joist $(s)=20$ in

$F_v^{\text{'}}=190$ psi

Joist span length $(I)=48$ in