A particle \(P\) moves in a straight line so that, at time \(t\) seconds, its acceleration \(a\) m s\(^{-2}\) is given by
$$a = \begin{cases}
4t - t^2, & 0 \leq t \leq 3, \\
\frac{27}{t^2}, & t > 3.
\end{cases}$$
At \(t = 0\), \(P\) is at rest. Find the speed of \(P\) when
- \(t = 3\), [3]
- \(t = 6\). [5]