Two black surfaces, AB and BC, of lengths $5$ m and $6$ m, respectively, are oriented as shown. Both surfaces extend infinitely into the third dimension. Given that view factor $F_{12}=0.5, T_{1}=800 K, T_{2}=600 K, T_{\text{surrounding}}=300 K$ and Stefan-Boltzmann constant, $\sigma =5.67 \times 10^{-8} W/ (m^{2}K^{4})$, the heat transfer rate from surface $2$ to the surrounding environment is _______ kW.
