Answer:
10,000 kg m/s
Step-by-step explanation:
The impulse exerted on an object is equal to the change in momentum of the object itself:

where
I is the impulse
F is the force applied
is the time during which the force has been applied
is the change in momentum
In this problem, we are already given the change in momentum of the rocket: since the rocket starts from rest, its change in momentum is equal to its momentum after 5 seconds,

and so, the impulse is equal to this value.