(Use of the McCabe-Thiele method) A mixture of di- and tri-ethylamines containing 55 mole% of the former is fed to a distillation column at a rate of 40 kmol/h. The feed is at its bubble point. The column is to operate at atmospheric pressure and the top product should not have more than 2.5 mol % of the less volatile. Also, not more than 2% of the diethylamine in the feed should be allowed to leave at the bottom. The reflux to the column is a saturated liquid. Determine (a) the minimum reflux ratio, (b) the number of theoretical plates if the actual reflux ratio is 1.4 times the minimum, (c) the slopes of the two operating lines, and (d) the number of theoretical plates if the reflux is a subcooled liquid at such a temperature that one mole of vapour is condensed for twenty moles of reflux. The equilibrium data in terms of the more volatile are: x 0.02 0.039 0.052 0.065 0.09 0.092 0.14 0.215 0.43 0.601 0.782 0.853 0.932 0.985 y 0.042 0.085 0.124 0.153 0.225 0.243 0.316 0.449 0.678 0.802 0.910 0.948 0.970 0.993