A Car on a Test Track Accelerates from 0 Ft/s

Essay

A car on a test track accelerates from 0 ft/s to 208 ft/s in 8 seconds. The car's velocity is given in the table below:
$\begin{array} { | c | c | c | c | c | c | c | c | c | c | } \hline t ( s ) & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\\hline v ( t ) ( f t / s ) & 0 & 18 & 47 & 77 & 104 & 132 & 163 & 184 & 208 \\\hline\end{array}$
(a) Find the car's average acceleration for the following time intervals:
(i) [4; 6]
(ii) [4; 5]
(iii) [3; 4]
(b) Estimate the car's acceleration at t = 4.