5.38
21 divided by 3.9 is 5.38 and the equation for acceleration is change in velocity divided by time
Last summer i went to barrier island.
hope this help
The velocity equation is 
Known facts:
- t = 3.83s
- a= -3.04
- intial velocity = 0
Plug into equation known quantities:

Thus the final velocity is -11.6432m/s
Hope that helps!