A point source isotropically emitting 108 fast neutrons per second falls out of its shield onto a railroad platform 3-m horizontally from the track. A train goes by at 60-miles per hour. Ignoring scattering and attenuation, what is the fluence of neutrons that would strike a passenger at the same height above the track as the source?

A point source isotropically emitting 108 fast neutrons per second falls out of its shield onto a railroad platform 3-m horizontally from the track. A train goes by at 60-miles per hour. Ignoring scattering and attenuation, what is the fluence of neutrons that would strike a passenger at the same height above the track as the source?