$($b$)$ A mixture containing $10\%($mole$)$ solute and rest inert is fed to a packed tower in which $90\%$ of the solute is absorbed$.$ Solute free water used for absorption contains $5\%($mole$)$ solute when it leaves

the tower at the bottom. If the equilibrium relationshio is $Ye=0\mathrm{.}05xe$ and $Hy=0\mathrm{.}5m$ and $Hx=0\mathrm{.}4m,$ what is the height of the packed section.