Figure 2 illustrates steady-state molecular energy transport through the walls of a spherical shell with constant thermal conductivity, k The inner shell is maintained at a constant temperature, T, by virtue of a self-contained electrical heater. The outer wall is effectively at the ambient temperature, T. T a R2 Heater Figure No 2 Spherical heated a Draft the shell volume element that represents the system where the transport of energy of taking place. i. Include all the relevant variables acting in the system State initial and boundaries conditions. [6 marks] b. Derive the temperature distribution in the outer shell of the sphere. [15 marks] c. Describe in words, an analogous problem in molecular mass transport using a sphere with constant diffusivity Das and concentration changing in the radius direction [4 marks] d. Write the corresponding expressions for the concentration distribution and compare each of the terms to demonstrate the analogy between both equations. [15 marks]