The Equilibrium Constant (K_c) for the Decomposition of Ammonium Hydrogen $\rightleftharpoons$

The equilibrium constant (K_c) for the decomposition of ammonium hydrogen sulfide, NH₄HS(s) $\rightleftharpoons$ NH₃(g) + H₂S(g) , is 1.8 × 10^-4 at 25 °C. If excess NH₄HS(s) is allowed to equilibrate at 25 °C, what is the equilibrium concentration of NH₃?

A) 3.2 × 10^-8 M
B) 9.0 × 10^-5 M
C) 1.8 × 10^-4 M
D) 6.7 × 10^-3 M
E) 1.3 × 10^-2 M