The position of a pinewood derby car was observed at various moments; the results are summarized in the following table. Find the average velocity of the car for (a) the first 1-s time interval, (b) the last 3 s, and (c) the entire period of observation.
$$
\begin{array}{lllllll}\hline t(\mathbf{s}) & {0} & {1.0} & {2.0} & {3.0} & {4.0} & {5.0} \\ \hline x(\mathbf{m}) & {0} & {2.3} & {9.2} & {20.7} & {36.8} & {57.5} \\ \hline\end{array}
$$