Given surface area of sphere, A=4m2 Temperature, T=400K Emissivity, ε=0.5 Environment temperature, T0=200K Sțefan Boltzmann constant, σ=567×10−8Wm−2K4 According to stefan Boltzmann law, rate of energy exchange of the sphere E=εσA(T4−T04) =0.5×5.67×10−8×4(4004−2004) =27216×103W=2721.6W