Question

A ball is dropped 2.75 m to the floor below. What is the acceleration of the ball while it is on the floor if it is on the floor for 0.0400 s?

I'm really confused on this question because it is a free fall question so wouldn't the acceleration be -9.81 m/s/s? How is the answer +340.0 m/s/s?

This is what I have but I don't know which equation to use...
y = -2.75 m
vi = 0 m/s
vf = ?
a = -9.81 m/s/s
t = 0.0400 s

Someone responded but I keep on getting the wrong answer. I'm getting 367.5 m/s/s and not +340.0 m/s/s.