Answer:
10800 kg m/s
Explanation:
Since the dumpster was initially at rest, its momentum before collision equal to zero. So that the total momentum of the car and dumpster before collision is 10800 kg m/s.
The principle of conservation of linear momentum states that: in a system of colliding bodies, total momentum is conserved. Therefore, the total momentum of the car and dumpster after collision is 10800 kg m/s.