After a drug is taken orally, the amount of the drug in the bloodstream after t hours is f (t) = 122(e^-0.2t - e^-t) units.

(a) Graph f (t), f′(t), and f″(t) in the window [0, 12] by [-20, 75]

(b) How many units of the drug are in the bloodstream after 7 hours?

(c) At what rate is the level of drug in the bloodstream increasing after 1 hour?

(d) While the level is decreasing, when is the level of drug in the bloodstream 20 units?

(e) What is the greatest level of drug in the bloodstream, and when is this level reached?

(f) When is the level of drug in the bloodstream decreasing the fastest?