A low radioactive material is used in biochemical process to induce biological mutation. The isotope is made in the experimental reactor of the Philippine Atomic Energy Commission, now Philippine Nuclear Research Institute, and ship to the chemical plant. It has a half-life of 8.06 days. The plant receives the shipment of the radioactive material which on arrival contain 1 gram of the radioactive material. The plant uses the material at the rate of 0.1 gram per week. Find the time it will take for the radioactivity to last.