Two thin radiation shields with emissivities of ε3 = 0.10 and ε4 = 0.15 on both sides are...

Two thin radiation shields with emissivities of ε3 = 0.10 and ε4 = 0.15 on both sides are placed between two very large parallel plates, which are maintained at uniform temperatures T1 = 700 K and T2 = 350 K and have emissivities ε1 = 0.6 and ε2 = 0.7, respectively. Determine the net rates of radiation heat transfer between the two plates with and without the shields per unit surface area of the plates, and the temperatures of the radiation shields in steady operation.