A person took some medicine but does not remember how much. Concerned that she took too much she has a blood test every hour for several hours. Time t is measured in hours since the first blood test and amount of medicine in her body, m, is measured in milligrams. She started out with 100 mg of medicine in her body. The milligram in her body decreases by 0.5 every hour. In how many hours will the person have no medicine remaining in the body?