Network Analyst Help

I'm going through the ESRI tutorial for the Network Analyst now so do
not yet have a feel for the utility of this extension for the task I'm
working on. If I give a brief description of the problem I'm working on

could someone tell me if this is easily done wtih Network Analyst?

Here goes:


I have two central locations that represent stores. I have lat and long

for all customers that visited either store. I need to determin the
travel time for each of the customers. In doing so I want to establish
the average drive time for the closest 80% of customers. Based on this
calculation I want to project a potential service area in a new city
based on a radius that represents the average drive time from the
previous location.


In order to use calculate drive times does the road layer have to have
distances, and speed limits? Or more generally, what values need to be
included in a road layer to calculate travel times? Does the ESRI
StreetMaps USA include the necessary attributes to calculate drive
times?


I know this is a lot. Any bits and pieces people could fill in would be

much appreaciated.


Thanks,
Aaron