The grpah is plotted with the number of strides along the x axis and the distance travelled along the y axis.
So, the slope of the graph gives the distance travelled by Robin per stride or the stride length. The approximate value of slope of the graph is,
[tex]\text{Slope}=\frac{\Delta y}{\Delta x}=\frac{8-0}{3-0}=\frac{8}{3}=2.67[/tex]So, the stride length or the unit rate of Robin is approximately 2.67 feet.