Four hundred lbmol/h of an equimolar mixture of n-heptane and toluene at 200 F and 20

Four hundred lbmol/h of an equimolar mixture of n-heptane and toluene at 200^οF and 20 psia is to be separated by extractive distillation at 20 psia, using phenol at 220^οF as the solvent, at a flow rate of 1,200 lbmol/h. Design a suitable two-column system to obtain reasonable product purities with minimal solvent loss.