A solution has [Ag⁺] of 3.2 × 10⁻³ M and 0.125 M NH₃. What is the concentration of Ag⁺ after the solution reaches equilibrium? The formation constant (Kf) of Ag(NH₃)₂⁺ is given as 1.7 × 10⁷.
A. 1.6 × 10⁻⁹ M
B. 6.8 × 10⁻⁴ M
C. 2.2 × 10⁻⁶ M
D. 1.3 × 10⁻⁸ M