Update: The numbers in this question are incorrect, please replace them in symbol to solve it, thanks a lot

(30%) A thermocouple inside a plastic rod. See below. Thermocouple can apply 0.5 (W/m) heat to metal. Radius of thermocouple and metal are Ri =0.02 (m) and R (m). thermal conductivity of plastic 0.2(W/m K), temperature at Ri is Ti =120 C , temperature at R is T=70 C. (a) Write down heat transfer equation inside the plastic by using shell balance. (b) Determine R. (c) Concern of convective heat transfer, temperature of air is 25 C, please calculate heat transfer coefficient