Determine the pH of the solution after the addition of 200 mL of HNO3.?

Update: A 100 mL sample of 0.1 M NH3 is titrated with 0.1 M HNO3. The Kb of NH3 is 1.8 x 10^-5
Update 2: The answer is 1.48. I am just unclear about how to obtain this answer. Thanks in advance!
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