Steel tubes (k=35 w/m2·k) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boiler to the turbine in a power plant. safety and economic concerns make it practical to add a 200-mm layer of insulation (k=0.1 w/m·k) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity ε=0.1. the air (with a convective coefficient h=5 w/m2·k) and wall temperatures of the plant are 27°c. if the inner surface temperature of the tube corresponds to the steam temperature, find the highest temperature, in °c, of the steam temperature.