## Precalculus (6th Edition) Blitzer

a. $t=\frac{1}{c}[ln\frac{A}{A-N}]$ b. about $20.5$ weeks.
a. We can rewrite the formula as $t=\frac{1}{c}[ln\frac{A}{A-N}]$ b. Given $A=65, N=30, c=0.03$, we have $t=\frac{1}{0.03}[ln\frac{65}{65-30}]\approx20.5$ weeks.