please help very confused. Flvs

Many doctors rely on the use of intravenous medication administration in order to achieve an immediate response of a particular drug's effects. The concentration, C. in mgIL. of a particular medication after being injected into a patient can be given by the function C(t) = -21'2 + 81', where the time, t, is hours after injection. k Part A: What are the domain and range of the function C(t) based on the context of the problem? Show all necessary catculations. (5 points) Part B: Graph the function to determine the greatest concentration of the medication that a patient will have in their body. (5 points)