The concentration of a drug in the body decreases exponentially after a dosage is given. In one clinical study, adult subjects averaged 15 micrograms/milliliter (mcg/mL) of the drug in their blood plasma 1 hr after a 1000-mg dosage and 4 micrograms/milliliter 7 hr after dosage. a) Find the value k, and write an equation for an exponential function that can be used to predict the concentration of the drug, in micrograms/milliliter, t hours after a 1000-mg dosage. b) Estimate the concentration of the drug 2 hr after a 1000-mg dosage. c) To relieve a fever, the concentration of the drug should go no lower than 3 mcg/mL. After how many hours will a 1000-mg dosage drop to that level? a) k= (Round to three decimal places as needed.) Choose the correct equation below. O A. P(t) = 20.700 e - 0.220t O B. P(1) = 18.7 e -0.220t O C. P(1) = 15 e - 0.220t O D. P(t) = 15 e - 0.100t O E. P(1) = 18.7 e - 0.340t OF. P(t) = 18.7 2 -0.4401 O G. P(t) = 16.700 e - 0.2201 OH. P(t) = 20.700 e - 0.440t b) The concentration of the drug after 2 hr will be about mcg/ml (Round to one decimal place as needed.) c) After about hr the concentration of the drug will have dropped to 3 mcg/mL. Round to the nearest integer as needed 1