For each of the following, indicate if the number of half-lives elapsed is: 1. one half-life 2. two half-lives 3. three half-lives a. a sample of ce-141 with a half-life of 32.5 days after 32.5 days b. a sample of f-18 with a half-life of 110 min after 330 min c. a sample of au-198 with a half-life of 2.7 days after 5.4 days