Graphical Solution for Minimum Reflux Ratio and Total Reflux. For the rectification given in Problem $11\mathrm{.}4-1,$ where an equimolar liquid feed of benzene andtoluene is being distilled to give a distillate of composition x $=0\mathrm{.}90$ and abottoms of composition x$,=0\mathrm{.}10,$ calculate the following using graphicalmethods.$($a$)$ Minimum reflux ratio Rm$($b$)$ Minimum number of theoretical plates at total reflux.Ans. $($a$)$ R$,=0\mathrm{.}91$; $($b$)4\mathrm{.}0$ theoretical trays plus a reboiler

I$\text{'}$m solving this question but the drawing is always $6$ trays where is my wrong step?