Answer:
vb = 22.13 m/s
Step-by-step explanation:
ma = 124 kg
mb = 13 kg
vi = 2.10 m/s
According to the property of conservation of momentum, and considering that, initially, both the astronaut and the bag moved together at 2.10 m/s:

The minimum final velocity of the bag, vb, the will keep the astronaut from drifting away forever occurs when va = 0:

The minimum final velocity of the bag is 22.13 m/s.