An analytical chemist is titrating 213.3 mL of a 0.5700 M solution of ammonia (NH₃) with a 0.08500 M solution of HNO₃. The p Kb of ammonia is 4.74. Calculate the pH of the base solution after the chemist has added 966.8 mL of the HNO₃. solution to it.

Note for advanced students: you may assume the final volume equals the initial volume of the solution plus the volume of HNO₃ solution added.
Round your answer to 2 decimal places. pH = ___