An electric furnace is designed to radiate 2.0×104W of thermal energy from its inner wall, which is maintained at 1.20×103K. The wall material has an emissivity of 0.80 and behaves as a diffuse radiator. What is the minimum total surface area of the wall?
a) 0.17m2
b) 0.26m2
c) 0.21m2
d) 0.14m2