Consider the Following Reaction, Equilibrium Concentrations, and Equilibrium Constant at a Particular

Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular temperature. Determine the equilibrium concentration of NO₂(g) . N₂O₄(g) ⇌ 2NO₂(g) K_c = 0.21 M
[N₂O₄]_eq = 0.068 mol L^-1

A) 1.9 mol L^-1
B) 0.12 mol L^-1
C) 0.60 mol L^-1
D) 0.028 mol L^-1
E) 0.036 mol L^-1