A solvent is recovered from a waste gas purification system with recycle. The gas feed contains 0.4 mol fraction of the solvent in an inert gas. The recovery unit gas effluent is to have a composition of 0.09 mol fraction solvent. The purification unit can remove 60% the solvent fed to it. What is the recycle ratio for the process, that is, how many moles of recycle are there per mol of waste gas fed to the process?

Please show all work. Really need to know how to work this problem.