mass trasfer . need help ASAP

Pertinent data on the binary system heptane-ethyl benzene are as follows: X 0 0.08 0.185 0.251 0.333 0.487 0.651 0.788 0.914 1.0 0.233 0.428 0.514 0.608 0.729 0.834 0.904 0.963 1.0 0 A feed mixture composed of 42 mol% heptane and 58 mol% ethyl benzene is to be fractionated to yield an overhead product of 97 mol% heptane and a residue of 99 mol% ethyl benzene. (a) Using a reflux ratio (L/D) = 1.5, determine the number of equilibrium stages needed for a saturated liquid feed and a bubble point reflux by the McCabe-Thiele graphical method. (23 marks) (b) Compute the minimum reflux ratio. (2 marks) (c) Determine the minimum number of equilibrium stages at total reflux (10 marks)