Two parallel disks of diameter $D=0\mathrm{.}6m$ separated by $L=0\mathrm{.}4m$ are located directly on top of each other. Both disks are black and are maintained at a temperature of $439$ K $.$ The back sides of the disks are insulated, and the environment that the disks are in can be considered to be a blackbody at $311$ K $.$

Determine the net rate of radiation heat transfer from the disks to the environment.

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