31. The concentration of a drug in the body can be modeled by the equation:

where is the dosage administered (mg), is the volume of distribution

(L), is the absorption rate constant (h–1), is the elimination rate constant

(h–1), and t is the time (h) since the drug was administered. For a certain drug, the following quantities are given: mg, L, h–1, and h–1.

(a) A single dose is administered at . Calculate and plot versus t for 10 h.

(b) A first dose is administered at , and subsequently four more doses are administered at intervals of 4 h (i.e., at ). Calculate and plot versus t for 24 h.