A mixture (total flow rate = 100 kmol/hr) with 28 mol% n-hexane, 42 mol% n-heptane, and 30 mol% of n-octane is to be distillated to produce a distillate product with 1 mol% of n-heptane and a bottoms product with 0.5 mol% n-hexane. The column operates at 1.2 atm with 60% of feed being in vapor state. At 1.2 atm, the relative volatilities of hexane and heptane with respect to octane are approximated to be 4.836 and 2.188, respectively. Calculate the number of equilibrium stages required to achieve this product specification at total reflux
a) 7
b) 8
c) 9
d) 10