$8-24$ Two perfectly black parallel planes $1\mathrm{.}2$ by $1\mathrm{.}2$ m are separated by a distance of $1\mathrm{.}2$ m$.$

One plane is maintained at $800$ K and the other at $500$ K$.$ The plates are located in

a large room whose walls are at $300$ K$.$ What is the net heat transfer between the

planes?