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 toluene 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 saturation 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 y 0.21 0.37 0.51 0.64 0.72 0.79 0.86 0.91 0.96 0.98 x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.95