The Amount of Medicine Present in the Blood of a Patient

Short Answer

The amount of medicine present in the blood of a patient decreases due to metabolism according to the exponential decay model. One hour after a dose was given, there were 3.7 nanograms/cm³ present, and a hour later there were 2.5 ng/cm³. After how many hours will there be less than 0.8 ng/cm³ present, assuming no more medication is taken? Round to 1 decimal place.