Consider a hot-water pipe 12-m in length and 8-cm in diameter. The pipe is to be buried in the soil below the ground surface. The outer surface temperature of the pipe is constant at 60C and the surface temperature of earth is constant at 2C. The thermal conductivity of soil is 0.9 W/m.C. If the rate of heat loss from the pipe is to be kept around 1000 Watts, determine the depth at which the pipe need to be buried.