A moving continuous perforated belt is used to leach soybean oil from soybean flakes. Hexane is used as solvent and is sprayed on the belt while moving in a countercurrent direction with the solid. The hexane is fed at $1kg$ hexane per $kg$ flakes. Determine the number of stages needed so that the soybean is leached from $25\%$ oil to $0\mathrm{.}5\%$ oil $($solvent$-$free basis$).$ Use both Ponchon $-$ Savarit method and McCabe $-$ Thiele method. Solution retention is measured as:

$\backslash$table$[[Wt\%$ oil in solution,$0,20,30],[kg$ solution retained,$0\mathrm{.}58,0\mathrm{.}66,0\mathrm{.}70],[kg$ insoluble solid,,,$]]$