Problem 3 (40 points] = . A mixture of benzene (ZA 0.4, aA = 2.312), toluene (zB = 0.25, QB - 1) and cumene (zc = 0.35, ac= 0.2202) is to be fractionated to recover 99.9% of benzene at the top and 99.5% of the toluene at the bottom. The reflux is a saturated liquid and the reflux ratio R = 2Rmin. If the feed is a mixture of 50% liquid and 50% vapor and if the feed flow rate is 100 moles/hr, answer the following: (a) Identify the light and heavy keys (b) Use Fenske's equation to estimate the minimum number of stages (c) Using the Underwood equation and Gilliland correlation, calculate the number of ideal stages re- quired for the separation and also find the feed stage. Use the Gilliland correlation in Figure 3. 1.0 N-Nmin N + 1 0.1 Van Winkle and Todd (16) o Gilliland data points [13, 14) Molokanov Eq. for line (17) A Brown-Martin data (15) 0.01 0.01 1.0 0.1 R-Rmin R + 1