I need to see the picture so I can answer
It's not clear to me what the given interval is supposed to be, so I'll use a generic one, [a, b] with a < b.
The average acceleration of the particle over this interval is given by the average rate of change of v(t),

The answer to your question is 0
9=m-4
9+4=m
13=m
9=13-4
9=9
I hope this answer helped you!!! Thank you!!!
A If im not mistaken but that is what i would go with