1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution With my solution, I think cold feed means ##q = \infty##, which is seen from my xy diagram. I have some issue understanding the statement "for each mole of feed 0.15 mol of vapor is condensed at the feed plate". I assumed that to mean that after the top stream goes through the condenser, 0.15 moles are sent back to the column in the split with the distillate stream. However, it became clear that my mass balance is wrong, since there are more moles of methanol coming from the distillate than is being fed, which does not make sense. So I don't really know what I am supposed to do with this critical piece of information.