SOLVED:The concentration of a drug injected into the bloodstream decreases with time. The intervals of time T when the drug should be administered are given by T=\frac{1}{k} \ln \frac{C_{2}}{C_{1}} where k is a constant determined by the drug in use, C_{2} is the concentration at which the drug is harmful, and C_{1} is the concentration below which the drug is ineffective. (Source: Horelick, Brindell and Sinan Koont, "Applications of Calculus to Medicine: Prescribing Safe and Effective Dosage," UMAP Module 202.) Thus, if T=4, the drug should be administered every 4 hr. For a certain drug, k=\frac{1}{3}, C_{2}=5, and C_{1}=2 . How often should the drug be administered?

Chapter 12

Inverse, Exponential, and Logarithmic Functions

Section 5

Common and Natural Logarithms