After a large number of drinks, a person has a blood-alcohol level of 200 mg/dL (milligrams per deciliter). If the amount of alcohol in the blood decays exponentially, and after 2 hours, 112.5 mg/dL remains, find an exponential model for the person's blood-alcohol level f(t) where t is the time in hours. Also, Use your model to estimate the person's blood-alcohol level after 4 hours. (Round your answer to one decimal place).