Solute A is to be removed from in inert gas B in a multi-stage countercurrent absorption tower. The gas enters the tower at a rate of 200kgmol/h and contains 20mol%A. The solvent enters the tower at a rate of 800kgmol/h and is initially free of solute. Determine (a) the concentration of the exiting gas stream and (b) the number of stages, if the exiting liquid stream contains 4mol% of A. the equilibrium data is y=4.2x