It is desired to produce an overhead product containing 80 mol % benzene from a feed mixture of 68 mol % benzene and 32 mol % toluene. The following methods are considered for this operation. All are to be conducted at atmospheric pressure. For each method calculate the moles of product per 100 moles of feed and the number of moles vaporized per 100 mol feed. 

(a) Continuous flash distillation. 

(b) Continuous distillation in a still fitted with a partial condenser, in which 55 mol % of the entering vapors is condensed and returned to the still. The partial condenser is so constructed that vapor and liquid leaving it are in equilibrium and holdup in it is negligible.