Toluene saturated with water at 30°C has 680 ppm H₂O and is to be dried to 0.3 ppm H₂O by fractional distillation. The feed is introduced to the top plate of the column and the overhead vapor is condensed, cooled to 30°C, and separated into two layers The water layer is removed, and the toluene layer, saturated with water, is recycled The average relative volatility of water to toluene is 120. How many theoretical stages are required if 0.25 mol of vapor is used per mole of liquid feed? (Neglect the change in L/V in the column.)