A cube 20 cm on a side is maintained at 80C and buried in a large medium

Question:

A cube 20 cm on a side is maintained at 80ºC and buried in a large medium at 10ºC with a thermal conductivity of 2.3 W/m· ºC. Calculate the heat lost by the cube. How does this compare with the heat that would be lost by a 20-cm-diameter sphere? Compare these heat transfers on a unit-volume basis.