Just out interest, what sort of transit is it?
I'm assuming that you are at least arriving by International since you mentioned *A. Are you also departing International or a Domestic flight? The reason why I ask is depending on what you are doing you may need to clear customs (and have a valid visa) to enter Australia, and if you are departing Internationally again you'd need to allow time for outbound customs. Depending on how long all that took, by the time you actually got anywhere interesting you may find you'd only have about an hour before you needed to get back to the airport.