A stream of ethane, n-butane, n-hexane, and n-heptane is to be separated using a flash drum operating at 250 kPa and 60C. The feed (100 kmol/h) is 15 % ethane, 20 % n-butane, 35 % nhexane, and 30 % n-heptane by mole. Calculate the composition and flow rates of the liquid and vapor products. Show calculations by hand for two trials and the result obtained by using Excel (or another software as appropriate).