A distillation column is operating under a vacuum. The column has 18 stages with the feed at stage 9, a partial reboiler, and a partial condenser. The pressure drop is 5.0 mm Hg in the condenser, 4.0 mm Hg in the reboiler, and 1.0 mm Hg per stage. The pressure of the condenser is controlled at 100 mm Hg. How do these pressure differences affect the separation? What is the pressure of the reboiler?