Heat and Mass Transfer
Kirchhoff's law states that

The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body
The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature
The wave length corresponding to the maximum energy is proportional to the absolute temperature
None of these

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Heat and Mass Transfer
A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,

The better insulation must be put outside
One could place either insulation on either side
The better insulation must be put inside
One should take into account the steam temperature before deciding as to which insulation is put where

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