answer part b please

11. A feed mixture having a composition of 40 mol\% n-butane 40 mol\% n-pentane, 15 mol\% n-hexane and 5mol%n-heptane is to be fractionated in a distillation column at 405.3kPa so that 95mol% of the n-pentane is recovered in the distillate and 95mol% of the n-hexane in the bottoms. The liquid teed at the boiling point is fed to the column at a flow rate of 1,000mol/h. a. Calculate the flow rates and the compositions of distillate and bottoms. [12 marks] b. Show that the boiling point of the feed is 74C. [8 marks]