## Calculus with Applications (10th Edition)

r = $\left[\frac{7}{3},4\right]$
$8 \leq 3r +1 \leq 13$ 1. Separate into two inequalities: $3r+1 \geq 8$ $3r+1 \leq 13$ 2. Solve the inequalities: $r\geq \frac{7}{3}$ $r \leq 4$ 3. Find the intersection to get your answer: r = $\left[\frac{7}{3},4\right]$