How Many Moles of HCl Need to Be Added to 150.0

How many moles of HCl need to be added to 150.0 mL of 0.50 M NaZ to have a solution with a pH of 6.50? (K_a of HZ is 2.3 $\times$ 10^-5) ? Assume negligible volume of the HCl.

A) 6.8 $\times$ 10^-3
B) 7.5 $\times$ 10^-2
C) 5.0 $\times$ 10^-1
D) 1.0 $\times$ 10^-3
E) none of these