An infinitely long furnace of 0.5 m x 0.4 m cross-section is shown in the figure. Consider all surfaces of the furnace to be black. The top and bottom walls are maintained at temperature T₁ = T₃ = 927°C while the side walls are at temperature T₂ = T₄ = 527°C. The view factor, F_1-2 is 0.26. The net radiation heat loss or gain on side 1 is ________ W/m. Stefan-Boltzmann constant = 5.67x10^-8 W/m²-K⁴.