A feed consists of the following components: 49% by mass of diisopropyl ether, 7.5% by mass of water and the rest isopropyl alcohol (IPA). This feed is mixed with pure water which will be used as fresh solvent during an extraction process to recover a maximum of the ether. The solvent enters at the top of the extraction unit and the feed is pumped from the bottom section to generate an ether eventually consisting of less than 3.2% IPA and an extracted IPA of a minimum composition of 25%, by mass. The whole extraction process will be run at a total constant pressure of 101.3kPa and at 27C. Apply the Hunter-Nash method to determine the number of actual stages which will be required for this extraction process involving diisopropyl ether, water and IPA if the average overall extraction unit stage efficiency is 60%. State any assumption(s) taken