For some applications, it is necessary to harden the surface of a steel above that of its interior. One way this may be accomplished is by increasing the surface concentration of carbon in a process called carburizing. Consider an FCC iron-carbon alloy with an initial concentration of 0.10 wt% C that is carburized in a furnace in which the atmosphere has a concentration of 1.10 wt% C. After 48 hours, the concentration of carbon 3.5 mm below the surface of the metal is 0.3 wt% C. At what temperature was the furnace operating?