ACME supplies prepackaged steel framed and sheathed storage buildings in kit form. The standard column used is a steel hollow round tube with a wall thickness of 0.4 inches fixed at both ends. A customer has requested a modification to a an existing package requesting that a floor to roof height of 26 feet from the 18 feet now furnished. If ACME wants to keep the factor of safety with respect to the critical load the same for 26 feet as it now provides for 18 feet, what is the minimum size (diameter) 0.4 inch wall thickness column ACME needs to provide in the package to this customer. 5 inch diameter used for 18 ft.