Liquid liquid extraction - worked solution

Worked Solution to the following problem: A feed solution contains 30 wt% C in A (and no B). This solution is extracted with pure B in a counter-current cascade of equilibrium stages to produce a final raffinate containing 10 wt% C. (a) On the basis of 100 kg/min of feed, find the number of equilibrium stages needed with a solvent rate of 34.51 kg/min. (b) What are the final extract and raffinate flowrates, and what is the final extract composition for (a) above.