2. A high temperature oven consists of three layers as shown in the figure below. The internal temperature of the oven is 1000C. The first layer is refractory material, the second layer is insulating layer, the third layer is steel. The thermal conductivity coefficients are kRM=2.8W/m.K,kins=1.2W/m.K and ksteel=42W/m.K, respectively. a) Derive an equation for TaTb, b) Determine the temperatures T0,T1,T2 and T3, c) Determine the overall heat transfer coefficient d) If it is desired to keep the outer surface temperature T3 at 60C, minimum insulation thickness should be increased by how much % so that the steel and refractory material thickness remains the same