Please solve

If a person takes a prescribed dose of 4 milligrams of Valium, the amount of Valium in that person's bloodstream at any time can be modeled with the exponential decay function A(t) = 4e -0-016t where t is in hours. a. How much Valium remains in the person's bloodstream 12 hours after taking a 4-mg dose? Round to 1 decimal place. mg b. How long will it take 4 mg to decay to 2 mg in a person's bloodstream? Round to 2 decimal places. hours c. At what rate is the amount of Valium in a person's bloodstream decaying 7 hours after a 4-mg dose is taken. Round to 3 decimal places. A' (7) mg/hr