Adsorption of phenol from its aqueous solution on to fly ash obeys Freundlich isotherm. At a given temperature, from $10 \mathrm{mgg}^{-1} \mathrm{and}^{16 \mathrm{mgg}^{-1}}$ aqueous phenol solutions, the concentrations of adsorbed phenol are measured to be $4 \mathrm{mgg}^{-1}$ and $10 \mathrm{mgg}^{-1}$, respectively. At this temperature, the concentration (in $\mathrm{mgg}^{-1}$ ) of adsorbed phenol from $20 \mathrm{mgg}^{-1}$ aqueous solution of phenol will be $\_\_\_\_$ . Use: $\log _{10} 2=0.3$