Help with TITRATION problem? urgent!!!?

A sample of 0.1309 g of an unknown monoprotic acid was dissolved in 25.0 mL of water and titrated with 0.0604 M NaOH solution. The volume of base required to reach the equivalence point was 19.9 mL. After 14.0 mL of base has been added to the titration, the pH was determined to be 5.21. What is the Ka of the unknown acid?