How Many Moles of Sodium Acetate Must Be Added to 500

How many moles of sodium acetate must be added to 500 mL of 0.25 M acetic acid solution to produce a buffer with a pH of 4.94? The pK_a of acetic acid is 4.74.

A) 0.011 moles
B) 0.021 moles
C) 0.125 moles
D) 0.198 moles
E) 0.206 moles