The graph you provided appears to be an inverted parabola. It is velocity vs time. That meas the motion is not uniformly accelerated. You cannot use the standard kinematics formulae. The maximum time is about 19 s (the image is fuzzy at the point). Now you need to find the equation of the velocity v(t).
since v(0) = 0, and v(19) = 0, you could model the velocity as v(t) = -kt(t-19) (Why negative sign in front of k?)
Use the given data and find the equation.
The displacement from point A to point B is going to be the inegral from A to B of v(t) = dx/dt.
Work out that part and let me know if you need more help.