A long steam pipehas an inner radius r; and an outer radius of r2. The pipe is covered with thermal insulation having an outside radius of r3. The temperature of the outer surface of the pipe, T2, and the are fixed. The energy loss per unit area of outside surface of temperature of the surrounding air, Too, the insulation can be described by the Newton rate equation. For such a case, determine the critical radius (the radius of the insulation associated with the maximum energy transfer).