(40 points) A hollow stainless bearing ball having inner radius ri=0.0080m and outer radius ro= 0.015m is at steady state in a ball bearing system. The temperature at the inner wall is Tl=20.C, and the temperature at the outer wall is To=35C. The thermal conductivity k=15W/mK for the stainless stecl. Conduction in the bearing ball only occurs radially ( r-direction), and there is no heat generation. The properties are constant. Analyze the system at steady state. (a) Starting from the governing heat diffusion equation, determine the simplified equation and find the general solution of the temperature profile T(r) in the hollow stainless sphere. (b) What are the boundary conditions needed to solve for temperature profile T(r) in part a? (c) Solve for the temperature profile in the insulation layer, T(r) expression. (d) What is the heat transfer rate qr at the outer surface of the hollow stainless sphere