The concentration of a drug in the body decreases exponentially after a dosage is given. In one clinicalstudy, adult subjects averaged 12 micrograms/milliliter (mcg/mL) of the drug in their blood plasma 1 hr after a1000-mg dosage and 5 micrograms/milliliter 7 hr after dosage.

a) Find the valuek, and write an

equation for an exponential function that can be used to predict the concentration of thedrug, inmicrograms/milliliter, t hours after a1000-mg dosage.

b) Estimate the concentration of the drug 6 hr after a1000-mg dosage.

c) To relieve afever, the concentration of the drug should go no lower than 2 mcg/mL. After how many hours will a1000-mg dosage drop to thatlevel?