A buffer solution was made by adding 85mL of a 0.8 M acetic acid solution and 80mL of a 0.31 M sodium acetate solution to a 500mL volumetric flask as well as diluting to the mark with distilled water. A reaction mixture was buffered with this solution by adding 40mL. The total volume of the reaction mixture is 100mL as well as the ionic strength is 0.2. Explain what is the hydrogen ion concentration of this solution?