Where y and x are concentrations of the peptide in the extract and raffinate, respectively in g/L. It is desired to extract at least 90% of the peptide from a feed stream having a peptide concentration of 3 g/liter. For a feed stream (F) at a flow rate of 5.0 liters/min and an extract stream (S) at a flow rate of 3 liters/min, graphically estimate how many equilibrium stages will be required for countercurrent extraction. What is the concentration of the peptide in the exit extract stream