B) An insulating powder is densely packed in the annular space between two concentric spheres with radii 75 mm and 50 mm The inner sphere is uniformly heated with electric power input of 30 W. Steady state temperature attained by inner sphere is 120C and that by outer sphere is 30C. Neglect thermal resistance offered by the material of the spheres. a) Calculate thermal conductivity of the powder. 0176 b) Calculate the thermal resistance offered by insulating powder- 3.01 L3/C