Suppose a piece of steel has no initial carbon but is subject to a surface concentration of 2.0 percent. The carbon at the surface will diffuse into the steel. It is desired to have a concentration of 9.400e-03 percent Carbon at a depth of 9.0 mm. If the process is to take 7.807e 07 seconds, at what temperature should the process occur (in Celsius)

In the winter, in order to keep the classroom steadily at 68 f before 10 pm, heating with an average rate of 42,000 btu/hr is provided. assume the outdoor temperature maintains at 32°f, determine the electrical power (kw) required to (a) operate a reversible heat pump (b) operate a real heat pump with a cop (7) of 4.5 and (c) operate an electrical-resistance heater.