feed to a distillation column contains $60$ kg$/$s of benzene $($B$)$ and $10$ kg$/$s of toluene $($T$),$ and a small amount of xylene $($X$).$ The distillate contains pure benzene. The bottom stream flow rate is $100$ kg$/$s$.$ Hundred percent of toluene in the feed ends up in the bottom. Draw and label the block flow diagram, and perform degree of freedom analysis.