The concentration of a drug in the body decreases exponentially after a dosage is given. In one clinical study, adult subjects averaged 13 micrograms/milliliter (mog/mL) of the drug in their blood plasma 1 hr alter a 1000mg dosage and 2 micrograms/milliliter 7 hr after dosage. a) Find the value k, and write an equation for anexponential function that can be used to predict the concentration of the dmg, in micrograms/milliliter, t hours after a TOGOmg dosage. lb) Estimate the concentration of the drug 6 hr after a 1000-mg dosage. c} To relieve a fever. the concentration of the drug should go no lower than 2 mcg/mL. After I how many hours will a moo-mg dosage drop to that level? ( a) k = D (Round to three decimal places as needed}