A steam pipe is covered with two layers of insulation as shown in the figure (radii, conductivities and temperatures on the figure). The inner surface of the pipe is at 250 °C and the outer surface loses heat by convection to air at 30 °C. For steady one-dimensional radial conduction, determine (a) the heat loss per metre length of pipe (answer in W/m), (b) the temperature T_{3} at the interface between insulation A and insulation B (answer in °C) and (c) the outer surface temperature T_{4} (answer in °C).