The magnitude of the change in momentum of the driver is -1066 kg•m/s.

Momentum is given by the product of mass and velocity. To calculate the magnitude of the change in momentum, we subtract the final momentum from the initial momentum. In this scenario, the final velocity is 0, because the driver was brought to rest by the airbag, and the initial velocity is 31 m/s. So, to calculate: Initial momentum = mass * initial velocity = 125 kg * 31 m/s = 3875 kg•m/s Final momentum = mass * final velocity = 125 kg * 0 = 0 The magnitude of the change in momentum is therefore = |final momentum - initial momentum| = |0 - 3875 kg•m/s| = 3875 kg•m/s. The closest option to 3875 kg•m/s from those given is 3900 kg•m/s. The other options (4.0 kg•m/s, 21 kg•m/s, 47 kg•m/s) are far too low. Thus, we choose 3900 kg • meters per second as the closest estimate.

47 kg • meters per second. The change in momentum is equal to the initial momentum minus the final momentum. In this case, the initial momentum is 125 kg x 31 m/s = 3875 kg m/s and the final momentum is 0 kg m/s. Therefore, the change in momentum is 3875 kg m/s. This is equal to the answer choice of 47 kg • meters per second.