Carbon is allowed to diffuse through a steel plate 15 mm thick. The concentrations of carbon at the two faces are 0.65 and 0.30 kg C/m³ Fe, which are maintained constant. If the preexponential and activation energy are 6.2 × 10^-7 m²/s and 80,000 J/mol, respectively, compute the temperature at which the diffusion flux is 1.43 × 10^-9 kg/m²-s.