Tung meal containing 55% oil is to be extracted at a rate of 4,000 kg per hour using n-hexane containing 5% wt oil as solvent. A counter current multiple stage extraction system is to be used. The meal retains 2 kg of solvent per kg of oil free meal while the residual charge contains 0.11 kg oil per kg oil free meal while the product is composed of 15 weight percent of oil. The theoretical number of ideal stages is

a. 4

b. 3

c. 5

d. 6