A distillation column with total condenser and partial reboiler is to be designed to fractionate a benzene-toluene mixture. The feed is a saturated liquid and contains 50% mole benzene and is you want to get a cap percent of 90% mole benzene and a residual with 10% mole benzene. If the reason for internal reflux in the area of rectification is 0.6. Determine according to McCabe's method Thiele:

1. External reflux ratio.

2. Number of theoretical stages and number of theoretical plates if it's fed on the optimal plate. What is the optimal feeding plate?