Calculate the rate of heat loss per foot and the thermal resistance for a 6-in. schedule 40 steel pipe covered with a 3-in. thick layer of 85% magnesia. Superheated steam at 300°F flows inside the pipe (hc = 30 Btu/h ft2 °F) and still air at 60°F is on the outside (hc =5 Btu/h ft2 °F).