At a Certain Temperature K for the Reaction 2NO₂

At a certain temperature K for the reaction 2NO₂ N₂O₄ is 7.5 liters/mole.If 2.0 moles of NO₂ are placed in a 2.0-liter container and permitted to react at this temperature,calculate the concentration of N₂O₄ at equilibrium.

A) 0.39 moles/liter
B) 0.65 moles/liter
C) 0.82 moles/liter
D) 7.5 moles/liter
E) none of these