A 5-cm outside diameter steel pipe is covered with a 0.6-cm layer of one insulation (k = 0.17 W/m-°C) followed by a 2.5-cm layer of a second insulation (k = 0.048 W/m-°C). The pipe surface temperature, Tp, is 315 °C, and the outer insulation surface temperature, To, is 40 °C. Write an expression for the heat transfer rate per unit length, Q/L , between the pipe surface temperature and the outer insulation surface temperature. Then, find the temperature at the junction of the two insulating materials.