An analytical chemist is titrating 51.7 mL of a 0.7400 M solution of diethylamine ((C₂H₅)₂NH) with a 0.09900 M solution of HNO₃. The pKb of diethylamine is 2.89. Calculate the pH of the base solution after the chemist has added 198.8 mL of the HNO₃ solution to it.