i honestly don't even know but yahoo answers says :
Impulse causes momentum to change, which means:
Impulse = change in momentum, or in equation form:
F∆t = (mv)2 – (mv)1
so p (impulse)= mass times velocity so the mass is 2,000kg and the velocity is 12,000N/5s.
speed is basically velocity so you have to calculate how many newtons per one second, so 12,000/5s-- just divide the numerator and denominator by 5. Also, velocity and speed are measured in N/s.