A 1000 L/min of a gas mixture containing 15% solute gas, 85% air by mole is to be treated in a gas absorption plate tower in order to recover 80% of the solute. Pure solvent enters the top of the tower at a rate of 40 mol/min. Operating conditions are 760 torr and 30^oC. Assume that the equilibrium relation is: Y=0.8X. Determine the number of ideal plates using the Kremser equation.