A vertical $3-$ft$-$high and $6-$ft$-$wide double$-$pane window consists of two sheets of glass separated by a $1-$in air gap at atmospheric pressure. If the glass surface temperatures across the air gap are measured to be $\backslash (65^\{\backslash$circ$\}\backslash$mathrm$\{$F$\}\backslash )$ and $\backslash (40^\{\backslash$circ$\}\backslash$mathrm$\{$F$\}\backslash ),$ determine the rate of heat transfer through the window by $\backslash (($a$)\backslash )$ natural convection and $\backslash (($b$)\backslash )$ radiation. The effective emissivity for use in radiation calculations between two large parallel glass plates can be taken to be $0\mathrm{.}82.$