Two parallel disks, 50 cm in diameter, are separated by a distance of 20 cm and completely surrounded by a large enclosure at 100C. The properties of the surfaces are T1 =600C, emissivity1=0.6, T2 =300C, emissivity2 =0.4. What is the net radiant heat transfer with each surface? (The disks emit radiation from front sides. Use view factor chart or correlation)