Final answer:
The total momentum of both astronauts before the collision is the sum of their individual momenta: 840 kg·m/s for the first astronaut and -300 kg·m/s for the second, resulting in 540 kg·m/s overall.
Step-by-step explanation:
The total momentum of both astronauts before they collide can be found by using the formula for momentum, which is p = m × v, where p is momentum, m is mass, and v is velocity. For the 70 kg astronaut moving at 12 m/s, the momentum is 70 kg × 12 m/s = 840 kg·m/s. For the 60 kg astronaut moving at -5 m/s (opposite direction), the momentum is 60 kg × -5 m/s = -300 kg·m/s. Adding both values gives us the total momentum before the collision, which is 840 kg·m/s + (-300 kg·m/s) = 540 kg·m/s. The correct answer is not provided in the options since the sum is 540 kg·m/s.