Astream of water containing a solute a at a concentration of 22.4 wt% kg-a/kg enters an extraction unit at a rate of 165 kg/h. a stream of pure solvent s enters the unit at a rate of 85.0 kg/h. in the unit, some of the a leaves the water stream and enters the solvent stream. a stream of water with some a and a stream of solvent with some a leave the unit. the ratio of the mass fraction of a in the solvent stream leaving the unit to the mass fraction of a in the water stream leaving the unit is 4.80. set up and solve the problem according to the procedure in section 4.3e.