Which of the following do you need to know to calculate impulse?

1. The problem statement, all variables and given/known data Before a collision, a 26 kg object is moving at + 10 m/s. Find the impulse that acted on the object if, after the collision, it moved at the following velocities. a) + 8.0 m/s b) - 8.0 m/s 2. Relevant equations Impulse = change in momentum = mass * change in velocity = m * (vf - vi) 3. The attempt at a solution a) = 26 (+10 m/s - + 8.0 m/s), impulse = 52? b) = 26 (+10 m/s - - 8.0 m/s), impulse = 468?