Cosmic ray bombardment of the atmosphere produces neutrons, which in turn react with nitrogen to produce radioactive carbon- Radioactive carbon- enters all living tissue through carbon dioxide (via plants). As long as a plant or animal is alive, carbon- is maintained in the organism at a constant level. Once the organism dies, however, carbon- decays exponentially into carbon- By comparing the amount of carbon- to the amount of carbon- one can determine approximately how long ago the organism died. (Willard Libby won a Nobel Prize for developing this technique for use in dating archaeological specimens). The half-life of carbon- is about years. In answering the following questions, assume that the initial quantity of carbon- is milligrams.