Question:   I was wondering how long it should take the smell of ammonia to reach a person six feet away. How long should it take for perfume to reach the person six feet away as well?

Answer:

You're not going to like this answer:  It's impossible to say for sure.

The type of problem you're trying to solve is inherently a statistical problem, which means that you can compute the probability that a molecule will be at some distance from the source at a given time, but not any certainty.  What I will say is that the rate of diffusion for an ideal gas is related to the size of the molecule and RMS velocity.  The mathematics for this process is a bit too complicated for your purposes, though your teacher may have given you a simplification of the equation to make your life easier.

From that standpoint, however, we can answer your second question.  Since the rate of diffusion depends on particle size/RMS velocity, we can guess that the organic molecules in the perfume, which are both heavier and larger than ammonia molecules, will most likely take longer to travel a given distance.