1 Evaluate the heat flux through a layer comprised of two materials. The top layer is 20m thick and has a thermal conductivity of 4W/mK. The underlying layer is 80m thick and has a thermal conductivity of k=10W/mK. The temperature at the surface (y=0m) is T(0)=0 and the temperature at y=100m is T(100)=5C. What is the heat flow at the surface (y=0m) when there is no radiogenic heating (i.e. H=0 )