A continuous fractionating column is required to separate a binary mixture containing 0.20 mole fraction of A into a top product of 0.95 mole fraction A, and a bottom product containing 0.02 mole fraction A. The feed is liquid at its boiling point. The vapour leaving the column is condensed but not cooled, and the reflux ratio is 9:1. The relative volatility (a ) remains constant at 1.85 and the vapour and liquid equilibrium data are in the form: y(1-x) = x(1 - y) Calculate: (a) the number of theoretical plates required; (b) the position of the feed plate