Consider a tube for transporting steam that is not centered properly in a cylindrical insulation material (k = 0.73 W/m∙K). The tube diameter is D1 = 20 mm and the insulation diameter is D2 = 40 mm. The distance between the center of the tube and the center of the insulation is z = 5 mm. If the surface of the tube maintains a temperature of 100°C and the outer surface temperature of the insulation is constant at 30°C, determine the rate of heat transfer per unit length of the tube through the insulation.