A steel gear made of 1018 steel (0.18 wt% C) is to be gas carburized at 927°C. If the carburizing…

A steel gear made of 1018 steel (0.18 wt% C) is to be gas carburized at 927°C. If the carburizing time is 7.5 h, at what depth in millimeters will the carbon content be 0.040 wt%? Assume the carbon content at the surface of the gear is 1.20 wt%. D (C in _ iron) at 27°C = 1.28 × 10_11 m2/s.