A thin aluminum sheet with an emissivity of 0.12 on both sides is placed between two very large parallel plates maintained at uniform temperatures of T₁ = 750 K and T₂ = 400 K. The emissivities of the plates are ε₁= 0.8 and ε₂ = 0.7. Determine the net rate of radiation heat transfer between the two plates per unit surface area of the plates, and the temperature of the radiation shield in steady operation.