Adsorption of phenol from its aqueous solution on to fly ash obeys Freundlich isotherm. At a given temperature, from 10 mg g⁻¹ and 16 mg g⁻¹ aqueous phenol solutions, the concentrations of adsorbed phenol are measured to be 4 mg g⁻¹ and 10 mg g⁻¹, respectively. At this temperature, the concentration (in mg g⁻¹) of adsorbed phenol from 20 mg g⁻¹ aqueous solution of phenol will be _____. Use: log₁₀ 2 = 0.3