An iron-carbon alloy initially containing 0.204 wts C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1100C. 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 0.0wtC. At what position will the carbon concentration be 0.153 wts after a 6 h treatment? The value of D at 1100C is 6.01011m2/s