One object is traveling northeast with a momentum of 12 kg-m/s, while a second object is traveling southwest on the same path as the first object with a momentum of 4 kg-m/s. When the two objects collide, they stick together. What is the momentum after their collision?(1 point)

16 kg-m/s northeast

16 kg-m/s southwest

8 kg-m/s northeast

8 kg-m/s southwest