The position of a pinewood derby car was observed at various times; the results are summarized in the following table. Find the average velocity of the car for (a) the first second, (b) the last 3s, and (c) the entire period of observation.



x = m ,t = s
x1 = m , t1 = s
x2 = m ,t2 = s
x3= m , t3 = s