A distillation column is separating methanol, ethanol, and butanol at a pressure of 2 atm. The column has a total condenser and a partial re-boiler. The feed is saturated liquid with the flow rate of 100 kmol/h comprising 45 mol% methanol, 30% ethanol, and 25% butanol. The external reflux ratio is 2.0, and the reflux is a saturated liquid. We desire a 98% recovery of ethanol in the distillate and a 99.1% recovery of butanol in the bottom product. The distillate product flow rate (D) in kmol per