4. A particle moving along thepositive x-direction with an initial velocity of 12 m/s is subjected to a retarding force that gives it a negative acceleration which varies linearly with time for the first 4 seconds as shown. For the next 5 seconds the force is constant and the acceleration remains constant. Plot the velocity of the particle during the 9 seconds and specify its value at t = 4 s. Also find the distance Ax traveled by the particle from its position at t = 0 to the point where it reverses its direction. a m/s²