Pipe with an OD of 6.03 cm and an ID of 4.93 cm carries steam at 250◦C. The pipe is cov- ered with 2.5 cm of magnesia (85%) insulation followed by 2.5 cm of polystyrene insulation (k = 0.025 W/m · K). The temperature of the exterior surface of the polystyrene is 25◦C. The thermal resistance of the pipe wa