Three infinitely long parallel plates 1, 2 and 3 are placed with 1 and 3 on the outer side and 2 placed in between them. Plates 1 and 3 are maintained at 1400 K and 400 K respectively. The emissivity of plates 1 and 3 is 0.4 and 0.7 respectively and that of plate 2 is the arithmetic mean of other two. Find the temperature of plate 2 (in K) if it does not receive any heat from any external source.
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