The drying and liquid-liquid extraction operations described in Problems 9,20b,C20885 on casende of Ideal gtage 3.18 and 3.19 , respectively, are examples of a flow configuration called a cros8of the cross-flow cascade that (Treybal, 1980) N=ln(S+1)ln[XNY0/mX0Y0/m] where S is the stripping factor, mVS/LS, constant for all stages, and N is the total number of stages. Solve Problem (3.19) using equation (3-69) and compare the results obtained by both methods. Answer: 78.1%