The gold-198 isotope is used in the treatment of brain, prostate, and ovarian cancer. Au-198 has a

Question:

The gold-198 isotope is used in the treatment of brain, prostate, and ovarian cancer. Au-198 has a half-life of 2.69 d. If a hospital needs to have 15 mg of Au-198 on hand for treatments on a particular day, and shipping takes 72 h, what mass of Au-198 needs to be ordered?