A vessel containing an equilibrium mixture of NO2(g) and N2O4(g) at a certain temperature and 1.00 b — Equilibrium Chemistry Question

A vessel containing an equilibrium mixture of NO₂(g) and N₂O₄(g) at a certain temperature and 1.00 bar total pressure is represented below.

Which is the best representation of the system at equilibrium after a certain amount of argon is added to the vessel, while keeping both the temperature and the total pressure constant?