The edge of long Au rod was covered at its edge with thin layer of radioactive Au. After the heating treatment at a constant temperature for 24 hours, the sample was cut into discs and the radioactive radiation from each disc was measured. Assuming that the intensity of the radioactive radiation is proportional to the concentration of the radioactive gold in the disc, and by using the table below calculate the self-diffusion coefficient of the Au. Radiation intensity 83.8 66.4 42 23.6 8.74 Distance from the rod edge [um] 10 20 30 40 50