An alloy initially containing 0.35wt%C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1127C. Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0wt%C. At what position will the carbon concentration be 0.15wt% after a 10h treatment? The value of D at 1400K is 6.91011m2/s