Correct Answer - A
Volume of sphere=Volume of cube
`(4pi)/(3)r^(3)=l^(3)`
`(r)/(l)=((3)/(4pi))^(1//3)` . . . (i)
`((dQ)/(dt))_(S)=4pir^(2)(T^(4)-T_(0)^(4))`
`((dQ)/(dt))_(C)=6l^(2)(T^(4)-T_(O)^(4))`
`((dQ//dt)_(S))/((dQ//dt)_(C))=(4pir^(2))/(6l^(2))`
Substitute r/l from equation (i), we have,
`=(4pi)/(6)xx((3)/(4pi))^(2//3)=((pi)/(6))^(1//3)`