Im so confused !!

Q1:

A drug trial is studying the efficacy of a new drug for thalassemia, a genetic disorder in which a patient is unable to properly synthesize the hemoglobin molecule in the blood. In the trial, the rate at which the drug is metabolized by the body is studied. The data from the trial is then used to construct a model for the drug’s metabolism. The concentration of a drug, in parts per million, in a patient’s bloodthours after the drug is administered is given by the function :

f(t)=t^5+ 3t^4- 6t³- 2t²+ 60t

a) What type of function is used to model the drug concentration?

b) What is the appropriate domain for this function?

c) We would like to determine when the drug is completely eliminated from the bloodstream. Find this value of time, t. Explain why anexactsolution to this problem is possible