When a drug is injected into a person’s muscle tissue, the concentration y of the drug in the blood is a function of the time elapsed since the injection. The graph of a typical time–concentration function f is given in Fig. 13, where t = 0 corresponds to the time of the injection.

At what time does f (t) attain its largest value?

in the units) Concentration blood (suitable 0.05 0.04 0.03 0.02 0.01 y y = f(t) t 6 7 8 9 10 11 12 13 Time (hours) Figure 13 Drug time-concentration curve. 1 2 3 4 5