The position of an object moving in a straight line is given by x = 7t - 5 t 2 + 3t 3, where x is in meters and t in seconds.

The position of an object moving in a straight line is given by x = 7t - 5 t ² + 3t ³, where x is in meters and t in seconds.
(a) What is the position of the object at t = 1s? 
  What is the position of the object at t = 2?
  What is the position of the object at t = 3?
What is the position of the object at t = 4 s? 

(b) What is the object's displacement between t = 0 and t = 4 s?
(c) What is the average velocity for the time interval from t = 2 s to t = 4 s?