can u tell me what formula i should be using to answer this question?

Question

If a stone falls past a bird on a ledge moving at 4 m/s, how fast will the stone be movingjust before it hits the ground below 9 seconds later?

A. 92.2 m/s
B. 48.2 m/s
C. 352.8 m/s
D. 36 m/s