A liquid containing 60 mol% toluene and 40 mol% benzene is continuously distilled in a single-equilibrium-stage unit

Question:

A liquid containing 60 mol% toluene and 40 mol% benzene is continuously distilled in a single-equilibrium-stage unit at atmospheric pressure. What percent of benzene in the feed leaves in the vapor if 90% of the toluene entering in the feed leaves in the liquid? Assume a relative volatility of 2.3 and obtain the solution graphically.