Answer :
I don't know if this question is worded incorrectly, but impulse is, by definition, the change in momentum. Thus, the change in momentum is 25 N*s.
If the impulse is 25 N-s, then so is the change in momentum.
The mass of the ball is extra, unneeded information.
Just to make sure, we can check out the units:
Momentum = (mass) x (speed) = kg-meter / sec
Impulse = (force) x (time) = (kg-meter / sec²) x (sec) = kg-meter / sec
