Use the References to access important values if needed for this question. Radioactive decay can be described by the following equation lnA=lnA0kt where A0 is the original amount of the substance, A is the amount of the substance remaining after time t, and k is a constant that is characteristic of the substance. For the radioactive isotope iodine-131, k is 8.62102days1. If the original amount of iodine- 131 in a sample is 38.3mg, how much time is needed for the amount of iodine131 that remains to fall to 28.3mg ? days