Problem 4 (20 points): A hollow metallic sphere (having an inner radius of 3.5cm, an outer radius of 5cm, and a thermal conductivity of 120W/m.K ) is wrapped from the outside with a thin material that generates heat at a uniform rate. Then, the thin material is covered with an insulating material having a thickness of 2cm and a thermal conductivity of 0.5W/m.K. The inner surface of the sphere is maintained at a temperature of 0C, and the whole system is exposed from the outside to air at a temperature of 25C. Assuming negligible contact resistances and that the heat transfer coefficient between the air and the outer surface of the insulating material is 5W/m2.K, 1. What is the power of the heat-generating material that would maintain a steady state temperature of this heat-generating material at 35.4C ? 2. What is the temperature of the outer surface of the insulating material at steady state