Is this correct?

The position of a particle as a function of time is given by x=(2.0 m/s)t + (-9.0 m/s^3)t^3.

(a) Plot x versus t for time from t=0 to t=1.0s

(b) Find the average velocity of the particle from t = 0.35 s to t = 0.45 s

(c) Find the average velocity from t = 0.39 s to t = 0.41 s

(d) Do you expect the instantaneous velocity at t = 0.40 s to be closer to 0.54 m/s, 0.56 m/s, or 0.58 m/s?

a)