Networks

hi, please i have series of question and i need your advice. i am trying to work on my assignment and i am to build a network even though it is supposed to be a WAN but im concentrating on the headquarters first. HQ is to have 3 departments which will have a total of 20-networked computers accessing accounts, web and e-learning servers. the man. dept only has access to the accounts server and the admin dept has access to update the web server.

1. im wondering if i can use 2 DMZ switches. is this possible?
2. do i put the servers and departments each on separate VLANs?

pls i really need to understand cuz im really confused