radioactice decay can be described by the gollowing equation

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 phosphorus-32, k is 4.85102 days 1. If the original amount of phosphorus-32 in a sample is 70.0mg, how much time is needed for the amount of phosphorus-32 that remains to fall to 34.7mg ? days