Two very long concentric cylinders of diameters D₁ = 0.35 m and D₂ = 0.5 m are maintained at uniform temperatures of T₁ = 950 K and T₂ = 500 K and have emissivities ε₁ = 1 and ε₂ = 0.55, respectively. Determine the net rate of radiation heat transfer between the two cylinders per unit length of the cylinders.