4) A mixture of hydrocarbons enters in a fractional distillation column to be separated. The fed mix has the following molar fraction composition : 0,42n-pentane; 0,18n hexane ; 0,25n-heptane and 0,15 n-octane. The bottom must contain maximum 3% mol of n-hexane and the top maximum 8%mol of normal heptane. Determine: (4 pts.). a) The heavy key component. b) The light key component. c) The composition of the distillated at bottom. d) The composition of the distillated at top