A 70kg driver moving at 15m/s relative to the road is brought to rest either by striking a rigid steering wheel or by an airbag. The rigid steering wheel stops the driver in 2.0ms, whereas the airbag stops the driver in 12ms. By approximately what percentage does the airbag reduce the magnitude of the average force on the driver compared with the rigid steering wheel?
a) 17%
b) 92%
c) 83%
d) 67%