Three concentric spheres of diameter 20, 30 and 40 cm are as shown. Innermost and outermost spheres have temperatures of 200 and 800 K respectively. Find temperature of intermediate sphere. Assume...

Three concentric spheres of diameter 20, 30 and 40 cm are as shown. Innermost and outermost spheres have temperatures of 200 and 800 K respectively. Find temperature of intermediate sphere. Assume perfect vacuum for annular spaces and emissivity = 0.2 for all spheres.