The Brown Gas NO₂ and the Colorless Gas N₂O₄ Exist

The brown gas NO₂ and the colorless gas N₂O₄ exist in equilibrium, 2NO₂ N₂O₄.In an experiment, 0.625 mole of N₂O₄ was introduced into a 5.00 L vessel and was allowed to decompose until equilibrium was reached.The concentration of N₂O₄ at equilibrium was 0.0750 M.Calculate K_c for the reaction.

A) 7.5
B) 0.125
C) 0.0750
D) 0.10
E) 0.050