After the Chernobyl accident, the concentration of 137Cs in milk was proportional to the concentration of 137Cs in the glass that cow consumed. The concentration in the grass was, in turn, proportional to the concentration in the soil. Assume that the only reaction by which 137Cs was lost from the soil was through radioactive decay and the half-life for this isotope is 30 years. Assume radioactive decay is a first-order process. Calculate the concentration of 137 Cs in cow's milk after 5 years if the concentration in milk shortly after the accident was 12,000 Bq per liter.