Consider coaxial, parallel, black disks separated a distance of L=0.20m. The lower disk of diameter D2=0.40m is maintained at T2=450K and the surroundings are at Tsur=310K What temperature, in K, will the upper disk of diameter D1=0.20m achieve if electrical power of 15W is supplied to the heater on the back side of the disk? T1=k