Liquid oxygen is stored in a thin walled, spherical container 0.8 m in diameter, which is enclosed within a second thin walled, spherical container 1.6 m in diameter. The opaque, diffuse, gray container surfaces have an emissivity of 0.05 and are separated by an evacuated space. If the outer surface is at 270 K and the inner surface is at 95 K, what is the mass rate of oxygen lost due to evaporation, in kg/s?