Answer: Peer-to-Peer architecture.
A Peer-to-Peer network would be sufficient enough to support all three of them. If Edward would set up a client/server network, then it will cost more and may become a problem if the main server will have a malfunction.
One of the good things about having a Peer-to-Peer network for a new company would mainly be the ability of each computer to have the same amount of access to the server files and all. Even if a single computer will have a problem, the other computers will still be able to access the network.