The equilibrium constant, Kc for the following reaction is 10.5 at 350 K.

2CH2Cl2 (g) ----> CH4 (g) + CCl4 (g)

If an equilibrium mixture of the three gases in a 12.8 L container at 350 K contains 0.397 mol of 2CH2Cl2 and 0.388 mol of CH4, the equilibrium concentration of CCl4 is M.