7.13. Separation of benzene and toluene. A column at 101 kPa is to separate 30 kg/h of a bubble-point solution of benzene and toluene containing 0.6 mass-fraction tolu- ene into an overhead product of 0.97 mass-fraction benzene and a bottoms product of 0.98 mass-fraction toluene at a reflux ratio of 3.5. The feed is sent to the optimal tray, and the reflux is at satura- tion temperature. Determine the: (a) top and bottom products and (b) number of stages using the following vapor-liquid equilibrium data. EQUILIBRIUM DATA IN MOLE-FRACTION BENZENE, 101 kPA y 0.21 0.37 0.51 0.64 0.72 0.79 0.86 0.91 0.96 0.98 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.95 x 0.1 0.2