Two thin radiation shields with emissivities of ε3= 0.1 and ε4= 0.15 on both sides are - placed between two very large parallel plates, which are maintained at uniform temperatures t= 600 k and t2=300 k and have emissivities ε1= 0.6 and ε2= 0.7, respectively. determine a)- the net rates of radiation heat transfer between the two plates with and without the shields per unit surface area of the plates. b)- the temperatures of the radiation shields in steady operation