Question about this picture....? plz help..ty?

Assuming that the ball is moving with constant acceleration, starting from the black circle, and the only force against it is the friction of 320N of the ground.

Using F = ma
-320 = 75 a
a = -4.27 m/s^2

Initial velocity (at the black circle), u = ???
Final velocity, v = 0 m/s
Displacement, s = 15 m

Using v^2 = u^2 + 2as
u^2 = 128
so u = 11.3 m/s (ans)