An asphalt road $(=3\mathrm{.}186$ x $10-7$ m$2$ s$-1)$ is initially at a uniform temperature of $50\backslash$deg C$.$ Suddenlythe road surface is reduced to $25\backslash$deg C by a downpour of rain. Determine the time required forthe temperature $27$ mm below the road surface to reach$35\backslash$deg C assuming the surfacetemperature remains constant at $25\backslash$deg C