Buffer solution problem: calculate the ph of a solution that is 0.30 m in hf and 0.15 m in naf?

For the question given above, I think there is a lack of information such as choice of answer for this question. Here is the solution for the question:
pKa = 3.14 
pH = pKa + log [F-] / [HF]
      = 3.14 + log 0.15 / 0.30
       = 2.84

pH is 2.84. I hope this answer helps.

The mass has escaped into a gas which you can not see so the law stays true.