A quality control chemist at Dow Chemical tried to determine purity of NaOH using titration.He measured out 0.500 g NaOH sample, and dissolved it in 20 mL water. 31.2 mL of a 0.386 mol/L HCl solution was used to reach the end point. Assume the impurity did not react with HCl, what is the %purity of this NaOH sample?