Help connecting 3 WAN's together

Okay, let's consider a mythical company, xyz corporation. It has three locations, two of which are regional offices and one is head office. Straight away, regardless of what business xyz corp does, we can identify some things they will use. There will be some sort of accounting system to track the money and that will be accessed by managers on all three sites. Straight away then we have one application that will need to use this WAN. Let's make another assumption, that the accounting system uses a server on each site so that all the users generate only local traffic to their server during the day, then the two regional servers pass data to/from the head office server during the night.
Secondly there might be a personnel system. We might assume that has a single server at head office but users at all three sites access it. That gives us a bit of real-time traffic across the WAN but we can assume it won't be much as there are few employees in personnel.
What else might there be? I'd say some sort of stock control/order processing system to track the manufacture of the product and the orders that have been placed for it. There will also be a company-wide email system and probably company-wide internet access, maybe from a single link to the internet at head office.
Think through the main functional elements of the company in this way and make sensible assumptions for each element of the business. That should give you a good starting point to work from. From there you can consider the hardware involved (we've already begun to do this above). Have a go at that then if you can, get a quick chat with your professor and ask if you're thinking along the right lines. And feel free to post back here for more help

I still haven't gotten anywhere...it is just basics that need to be brought up, like routers, switches, cabling, what equiptment and hardware needs to be used...so I appreciate the help but I think it may have gone over and above my head when it comes to the answer to this assignment.

Okay, maybe we should step back a bit.
Try having a look at www.cisco.com/en/US/docs/internetworking...ook/Frame-Relay.html for an introduction to Frame Relay. Keep reading even if there are bits you don't understand; there's a nice diagram further down that shows Frame Relay over a fractional T1 line that might be useful to you.
That gives you an idea of the WAN technology they've asked you to use. What you need then are routers that support Frame Relay (google will be your friend here, or search the Cisco site).
Finally I was a little confused by your PM; are you being expected to design the local LANs as well, or can you assume they are already there?

I am still re-emphasising not to forget security, because these days what ever you build you build it with security in mind from the scratch, whether softwares of networks

note : security acount for more than 50% expenditure in many mordern networks,so since this network will be imaginary make a lot of provision for security.

Thanks guys for the help. I turned it in and got an A. I just kept it simple and the basics that you needed to complete the network (like cabling and routers, switches..). But thank you! I am sure I will have more questions to come.

Way to go! Well done