Radioactive decay can be described by the following equation lnA=lnA0kt where A0 is the original amount of the substanco, 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 lead-214, k is 2.59102 minutes 1. If the original amount of lead-214 in a sample is 54.3mg, how much lead-214 remains after 28.4 minutes have passed? mg