At T(K), the partial pressures of SO2,O2 and SO3 are 0.662, 0.100 and 0.331 atm, respectively for the reaction 2SO2(g)+O2(g)⇌2SO3(g) at equilibrium. What is the partial pressure in atm, of O2 when the equilibrium partial pressures of SO2 and SO3 are equal at the same temperature ?