Answer
$V_{A}=-20\space km/h$
$V_{B}=10\space km/h$
$V_{C}=40\space km/h$
Work Step by Step
The slope of the line for a given segment is the average velocity for each segment. So we can write,
$V_{A}=\frac{10\space km-40\space km}{1.5\space h-0\space h}=-20\space km/h$
$V_{B}=\frac{20\space km-10\space km}{2.5\space h-1.5\space h}=10\space km/h$
$V_{C}=\frac{40\space km-20\space km}{3\space h-2.5\space h}=40\space km/h$
