A 1.35 mol sample of NO₂(g) is added to a 2.25 L vessel and heated to 500 K. The reaction N₂O₄(g) ⇌ 2NO₂(g) is at equiLiBrium with a concentration of [NO₂] = 0.513 at 500 K. Calculate the concentrations of NO₂(g) and N₂O₄(g) at equiLiBrium.