Calculate Ps$.$ Pnax. R$,($max$),$ R ald, and max $($ald$)$ for a rectangular section that has a width of b $12$ in$.$

$(300$ mm$)$ and an effective depth of d $=20$ in$.(500$ mm$)$ for the following cases:

a$.$ f $=3$ ksi.f$,=40$ ksi, A$,=$ four no$.8$ bars