You have 8 cups of flour. it takes one cup of flour to make 24 cookies. the function c(f)=24f represents the number of cookies, c, that can be made with f cups of flour. what domain and range are reasonable for the function?

You cannot make negative cookies so (c(f) and f)≥0.  And since cookies must (or at least should be in the real world) integers, f must be a multiple of 1/24. (otherwise you'd have fractional cookies).  What is a "reasonable" upper bound for c(f) is very subjective, obviously we cannot make an infinite amount of cookies :)

Because of this, the designer of this question, did so quite poorly.  Now simplistically we could say that the domain would be [0,+oo) and the range [0,+oo), But this would be ignoring all of the above.  In reality the domain would be [0, 1/24, 2/24, etc n/24]  where n/24 was some real limitation on the amount of flour (and time) that you could possibly have and the range would be [0,1,2,3,...n] where n would be the result of the the limited domain values.  (unless we were making fractional cookies :P)

Sorry, I could not resist, I cringe when I see subjective math problems.  The range and domain I put is what I would call "reasonable" range and domain.  I wonder what the designer of the question thinks is reasonable