4. A liquid feed to a distillation tower at 500kPa has compositions of n-butane (0.30),n pentane (0.35), n-hexane (0.20) and n-heptane (0.15). The liquid feed of 400mol/h at the boiling point (850C) is to be fractionated so that 95% of the n-pentane is recovered in the distillate and 95% of the n-hexane is recovered in the bottoms. The relative volatilities of the LK to the HK at the top and the bottom of the tower are assumed to be 6.25 and 4 respectively. A) Calculate the flow rates and the composition of distillate. [ 5 marks] B) Calculate the flow rates and the composition of the bottoms. [ 5 marks] C) Calculate the minimum number of theoretical stages. [ 3 marks]