a feed mixture containing $45$mole$\%$ benzene and rest toluene is to be separated into an overhead product containing $95$mole$\%$ benzene and a residue of $5$mole$\%$ benzene feed is a saturated liquid at its boiling point and is admitted to the columns at the rate of $120$ tons$/$day$.$ A refliux ratio of twice the minimum is to be used. Design a suitable bubble cap column.