What Is the Maximum Concentration of Mg²⁺ Ion That Can

What is the maximum concentration of Mg²⁺ ion that can exist in a 0.10 M NaF(aq) solution, without precipitating any magnesium fluoride? The K_sp of MgF₂ is 6.6 × 10^-9.

A) 1.3 × 10^-7 M
B) 6.6 × 10^-9 M
C) 6.6 × 10^-8 M
D) 1.6 × 10^-7 M
E) 6.6 × 10^-7 M