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