A mixture of A and B is flashed before it enters a distillation column. The mixture is 50mol% A and flows at 1000kmol/h. It is heated in a flash unit so that 70% of the mixture is vaporized before it enters the distillation column. The products from the flash unit are fed to the distillation column. The column contains a total condenser and a partial reboiler. The distillate has 95%A and the bottom product should not contains more than 2% of A. The reflux ratio is 3. Deternine the find the number of stages. The vapor liquid equilibrium date is shown in figure 2