This problem involves radiation, which requires the use of absolute temperature,
and thus all temperatures should be expressed in Kelvin. Alternately, we
could use °C for all temperatures provided that the four temperatures in the radiation
terms are expressed in the form (T 273)4. Substituting the given
quantities, the system of nine equations for the determination of nine unknown
nodal temperatures in a form suitable for use with the Gauss-Seidel iteration
method becomes