A billet of Iron is exposed to a source of carbon at a concentration of 2.2 kg/m3. Considering the diffusion coefficient of 7.28×10-12 m2/s, how long will it take for carbon concentration in iron to reach a value of 0.3 kg/m3 at a depth of 0.6 mm below the surface? Iron has 0.02 kg/m3 concentration of carbon in its composition.