The schematic represents a concentrically$-$braced simple frame. Webs of the wide flange beam $($AB$)$ and columns $($AC$,$ BD$)$ are in the plane of the structure. The slender braces $($AD$,$ BC$)$ are ineffective in compression because they buckle elastically under very low loads. All steel is A$572$ Grade $50.$ Bolted connections are shear$-$bearing, with threads of the bolts included in shear planes. Bolts are $\frac{7}{8}$ in Grade A$325$ in standard holes. For welded connections, the shielded$-$metal arc welding process is used with E$70$ electrodes.

If a concrete slab provides continuous lateral bracing for beam $AB,$ what is most nearly the lightest safe wide flange shape for beam $AB?$

A$.$ LRFD: W$2144$

B$.$ LRFD: W$1474$

C$.$ LRFD: W$2155$

D$.$ LRFD: W$1855$