At 800 K a reaction mixture contained 0.5 mole of SO2. 0.12 mole of O2 and 5 mole of SO3 at equilibrium. Kc for the equilibrium 2SO2+O2⇌2SO3 is 833 lit/ mole. If the voiume of the container is 1 litre, calculate how much O2 is to be added at this equilibrium in order to get 5.2 moles of SO3 at the same temperature.