I have been working on this problem all day and i just cant get the answer. Please help I would really appretiate it.

The position of a 230 g object is given (in meters) by x = 4.9t^3 - 8.0t^2 - 44t, where t is in seconds.
1. Determine the net rate of work done on this object at t = 2.1 s.
2. Determine the net rate of work done on this object at t = 3.9 s.
3. What is the average net power input during the interval from t = 0s to t = 2.1s ?
4. What is the average net power input during the interval from t = 2.1s to t = 3.9s?

Please help!!!