20 mL of a solution of acetic acid required 28.4 mL of 0.1 M NaOH for its neutralization. A solution ( X ) was prepared by mixing 20 mL of the above…

$\displaystyle 20$ mL of a solution of acetic acid required $\displaystyle 28.4$ mL of $\displaystyle 0.1$ M NaOH for its neutralization. A solution $\displaystyle (\mathrm{X})$ was prepared by mixing $\displaystyle 20$ mL of the above acetic acid and $\displaystyle 14.2$ mL of $\displaystyle 0.1$ M NaOH solution. What is the pH of the solution (X)? $\displaystyle \left(\mathrm{pK}_{\mathrm{a}}\right.$ value of acetic acid is $\displaystyle 4.75 )$.