An aqueous feed solution of $350k\frac{g}{h}$ containing $25wt\%$ acetone $($A$)$ and $75wt\%$ water $($B$)$ is

being extracted in a countercurrent multistage extraction system using $750k\frac{g}{h}$ pure methyl

isobutyl ketone $($C$)$ solvent at $298-299K.$ The outlet water raffinate will contain $5\mathrm{.}0wt\%$

acetone. Calculate the number of stages required by using the equilibrium data in below.