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   Radiation between equal area flat plates.
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   Form:
   [Nb, q] = RadBFp( epsilon, T1, Tn )
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   ------
   Inputs
   ------
   epsilon     (1,:)  Vector of emissivities
   T1          (1,1)  Temperature of first surface (°K)
   Tn          (1,1)  Temperature of nth surface (°K)

   -------
   Outputs
   -------
   Nb          (1,1)  Equivalent black plates
   q           (1,1)  Heat flux

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