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

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

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