An isotropic point source of neutrons emits 10E8 fast neutrons per second. It is 3m horizontally away from a train track. A train goes by at 60 miles per hour. Ignoring scattering and attenuation, what is the fluence (i.e. neutrons per meter square) of neutrons that would strike a pasenger at the same level with the source? These are the details of a problem, and I feel that it is simpler that I believe it to be, but I cannot take the first step. What would be some assumptions if any that I should make, in order to go about solving the problem?