Two Structural A$36$ steel $)=29{10}^3$ksi,${}_y=(36$ksi pipes that serve as posts must support a load as shown. The piping used has an outer diameter of $2\mathrm{.}375$ in and a wall thickness of $0\mathrm{.}109in.$ At the top and bottom the $18-ft$ pipes fit loosely into supports that prevent lateral motion but permit rotation. Determine the maximum allowable vertical force $F_0$ that can be tolerated if the factor of safety against buckling is to be $3.$