A face centered cubic (FCC) iron (Fe)carbon (C) alloy initially containing 0.20 wt% C is carburized at an elevated temperature and in an atmosphere in which the surface carbon concentration is maintained at 1.0 wt%. If after 49.5 h the concentration of carbon is 0.35 wt% at a position 4.0 mm below the surface, determine the temperature at which the treatment was carried out. D0 and Qd for the diffusion of C in FCC Fe are 2.3 x 10-5 m2 /s and 148,000 J/mol, respectively.