A person with a certain liver disease first exhibits larger and larger concentrations of certain enzymes (called SGOT and SGPT) in the blood. As the disease progresses, the concentration of these enzymes drops, first to the pre-disease level and eventually to zero (when almost all of the liver cells have died). Monitoring the levels of these enzymes allows doctors to track the progress of a patient with this disease. If C = f(t) is the concentration of the enzymes in the blood as a function of time,
(a) Sketch a possible graph of C = f(t).
(b) Mark on the graph the intervals where f' > 0 and where f' < 0.
(c) What does f¨(t) represent, in practical terms?