The structural formula shown is para-hydroxybenzoic acid, a weak diprotic acid used as a food preservative. Titration of 25.00 mL of a dilute aqueous solution of this acid requires 16.24 mL of 0.0200 M NaOH to reach the first equivalence point. The measured pH after the addition of 8.12 mL of the base is 4.57; after 16.24 mL, the pH is 7.02. Determine the values of pK_a1 and pK_a2 of para-hydroxybenzoic acid and the pH values for the two equivalence points in the titration.

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H-O- O || -C-0-H