i understand how they are getting an initial velocity of 4 but i am confused on how they get a final velocity of 6

.. . . . . . . . . Applied Force (N) O O N. Time (s) A force is applied to a 2 kg object, and measurements of the force as a function of time are shown. The force is the only force exerted on the object and is applied in the direction of the object's velocity. Which of the following could represent the initial velocity, vo. and the final velocity, vy, of the object? 4 m/s 6m/s 6m/s 4m/s