As I can see it , there are 4 straight lines. So here is what i suggest :-
Write the equations to each of these 4 lines. So you have 4 equations f(x,t) (x- distance and t - time)
now for each find dx/dt .
So now you have the velocity function (v=dx/dt) with the corresponding time limits, for example the first line goes from t=0 to t=15
Plot the 4 velocity functions accordingly.
Hope that helps !
For the period 0-15 sec
For the period 15-25 sec or for this 10 sec
V=(65-25)/10= 4, V=4m/sec
For the period 25-30 sec , there is no change in displacement hence, V=0
For the period 30-40 sec
V=(65-0)/10, V= 6.5m/sec
Now draw the V and t coordinate axes
and plot these points.....you have the answer