Sulfur dioxide and oxygen in the mole ratio 2:1 were mixed at a constant temperature of 1110K and a constant?

Sulfur dioxide and oxygen in the mole ratio 2:1 were mixed at a constant temperature of 1110K and a constant pressure of 9atm in the presence of a catalyst. At equilibrium, one-third of the sulfure dioxide had been converted into sulfur dioxide. Calculate the equilibrium constant Kp for this reaction under these conditions.