A horizontal plate, 25 by 50 cm, is maintained at a constant temperature of 78C and buried

Question:

A horizontal plate, 25 by 50 cm, is maintained at a constant temperature of 78ºC and buried in a semi-infinite medium at a depth of 5 m. The medium has an isothermal surface maintained at 15ºC and a thermal conductivity of 2.8 W/m · ºC. Calculate the heat lost by the plate.