What Will Be the PH of the Solution When 0

What will be the pH of the solution when 0.10 mol of H⁺ ion is added to a 2.0 liter buffered solution composed of 0.45 M ammonia,NH3,and 0.26 M ammonium fluoride,NH₄F? (K_b for ammonia = 1.8 × 10^-5)

A) 8.07
B) 4.63
C) 9.37
D) 10.34
E) 4.85