Fifty thousand kg/h of flaked soybeans, containing 20 wt% oil, is leached of oil with the same flow rate of n-hexane in a countercurrent- flow system consisting of an ideal leaching stage and three ideal washing stages. Experiments show the underflow from each stage contains 0.8 kg liquid/kg soybeans (oil-free basis).

(a) Determine % recovery of oil in the final extract. 

(b) If leaching requires three of the four stages such that one-third of the leaching occurs in each stage, followed by one washing stage, determine the % recovery of oil in the final extract.