A buffer has a HF concentration of 025 M and a pH of 418 Wha

A buffer has a HF concentration of 0.25 M and a pH of 4.18. What must the concentration of the NaF, in M, be ? (Refer to your textbook appendix for Ka or Kb values.) I don\'t know the Ka or Kb values :/ The NaF concentration must be________M.