12. The function below can be used to model the rate of decay of a medication in the blood stream based on the amount of time that has passed since the patient took the medication. f(x)=315(1.05)^x Which of the following answer choices represents the meaning of the a value from the function?
Which of the following answer choices represents the meaning of the b value from the function?

A) The amount of medicine left in the patient’s blood stream.
B) The initial amount of the medication taken by the patient.
C) The amount of time that passes between measurements of the medication in the patient’s blood stream.
D) The rate of decay of the medication amount in the patient’s bloodstream.