Keeping the Brain Cells Active

[doctorwayne]

Spock never lies!

I'll go with Smith.

That's correct.

The businessman living nearest to the engineer is Smith and the engineer's income is exactly a third of his. Therefore, this businessman cannot be the brakeman's namesake as the latter earns $3500 which is not divisible by three. Hence, the brakeman's name is not Smith. Neither is the fireman's name Smith, since railway man Smith beats him at billiards and so must be a person with a different name. This leaves the engineer to whom the name Smith may be correctly applied, thus answering the question.