A 100` diameter x 30` high oil storage tank is being inspected according to API Standard 650. The maximum out-of-plumb distance from the top of the shell relative to the bottom of the shell shall be determined by using what ratio?

A 100` diameter x 30` high oil storage tank is being inspected according to API Standard 650. The maximum out-of-plumb distance from the top of the shell relative to the bottom of the shell shall be determined by using what ratio?