A particle moves along a line with x = t³ - 9t² + 24t (SI units)…

Step 1. At rest. $v = 3(t - 2)(t - 4) = 0$ at $2\ \text{s}$ and $4\ \text{s}$.

Step 2. Acceleration. $a = 6t - 18$; at $4\ \text{s}$, $a = 6\ \text{m/s}^2$.

Step 3. Positions. $x(0) = 0$, $x(2\ \text{s}) = 20\ \text{m}$, $x(4) = 16$, $x(5\ \text{s}) = 20\ \text{m}$.

Step 4. Distance. $20\ \text{m} + 4\ \text{m} + 4\ \text{m} = 28\ \text{m}$.