What is the initial concern about this network, and What is the best way to secure it?

(private alea) Engineering hosts 172.16.5.2-255 Public area of DMZ ftp www server (name: Internet) 172.16.1.2 Internet (Insecure Puglic Screen (name: guarda) 172016.5.1 Scroon namco guard) 1720lbold (private area) Corplate hosts 172.16.3.2-255 (Private calea) Adminstration Station T72.16.20113 (Private area) Sales hosts 172.16.4.2-225