What is the corresponding equilibrium law expression?

Question

Once you have balanced the following chemical equation, find the correct corresponding equilibrium law expression:

Ag₂CO_3(s)  ↔ Ag_(s)  + CO_2(g)  + O_2(g) 

Answer 1

2Ag₂CO_3(s)  ↔ 4Ag_(s)  + 2CO_2(g)  + O_2(g)  ... balanced equation

Keq = [CO₂]²[O₂] (note: species present in the solid phase are not included in the equilibrium expression)