What is the ph of the buffer after the addition

Question

(a) Consider a buffer that is 0.153 M in lactic acid and0.167 M in sodium lactate. What is the pH of the bufferafter the addition of 0.0210 mol of NaOH to 1150. mL of buffer? Youmay assume that there is no volume change upon addition of thebase. pK_a(lactic acid) = 3.85.

(b) Consider a buffer that is 0.218 M in ammonia and 0.113M in ammonium chloride. What is the pH of the buffer afterthe addition of 0.0150 mol of HCl to 850. mL of buffer? You mayassume that there is no volume change upon addition of the acid.pK_b(ammonia) = 4.75.