Two parallel disks, 60 cm in diameter, are separated by a distance of 15 cm and completely surrounded by a large enclosure at 100°C. The properties of the surfaces are T₁ = 540°C, ∊₁ = 0.7, T₂ = 300°C, ∊₂ = 0.5. What is the net radiant heat transfer with each surface? (Do not include back side exchange, only that from the surfaces facing each other.)