The PH of a 0

The pH of a 0.15 M aqueous solution of NaZ (the sodium salt of HZ) is 10.7. What is the K_a for HZ?

A) 8.9 × 10^{- 4}
B) 3.3 × 10^{- 8}
C) 1.3 × 10^{- 12}
D) 1.6 × 10^{- 6}
E) 6.0 × 10^{- 9}