An analytical chemist is titrating 145.1mL of a 0.6400M solution of propionic acid HC2H5CO2 with a 0.8100M solution of KOH. The pKa of propionic acid is 4.89. Calculate the pH of the acid solution after the chemist has added 128.3mL of the KOH solution to it.

Note for advanced students: you may assume the final volume equals the initial volume of the solution plus the volume of KOH solution added. Round your answer to 2 decimal places.

pH=_________