Two large parallel plates having a gap of 10 mm in between them are maintained at temperatures T₁, = 1000 K and T₂ = 400 K. Given emissivity values, ε₁ = 0.5, ε₂ = 0.25 and Stefan-Boltzmann constant σ = 5.67 × 10^-8 W/ m²K⁴, the heat transfer between the plates (in kW/m²) is ______