$8-25$ Two parallel disks, $60$ cm in diameter, are separated by a distance of $15$ cm and

completely surrounded by a large enclosure at $100$C$.$ The properties of the surfaces

are T$1=540$C$,1=0\mathrm{.}7,$ T$2=300$C$,2=0\mathrm{.}5.$ What is the net radiant heat transfer

with each surface? $($Do not include back side exchange, only that from the surfaces

facing each other.$)$