A CFC-iron piece is subjected to an atmosphere rich in carbon (CO2) so that, through the diffusion of this gas (consider carbon as the main diffuser), it is given a hardness close to that of 316 -steel. Knowing that the concentration of carbon already present in this piece of iron is 0.025% by weight, and that the concentration of the gas on its surface remains constant and equal to 5.5%, determine the concentration of carbon at depth of 0.8mm in this piece after 6.5 hours of exposure to a temperature of 970C