Calculate the Equilibrium Concentration of Zn²⁺(aq) in a Solution That $\leftrightarrow$

Calculate the equilibrium concentration of Zn²⁺(aq) in a solution that is 0.0125 M Zn(NO₃) ₂ and 0.600 M NH₃.
Given: Zn²⁺(aq) + 4 NH₃(aq) $\leftrightarrow$ Zn(NH₃) ₄²⁺(aq) K_f = 2.9 * 10⁹.

A) 7.8 *10 10^-12 M
B) 4.7 *10 10^-11 M
C) 1.5 *10^-8 M
D) 2.5 * 10^-9 M
E) 2.9 * 10⁹ M