Choosing Server for SharePoint, Exchange, Active Directory, SQL

Hello

We want to migrate from work-group type network and setup an interoffice mail server and ,  ... with SharePoint, Exchange, outlook. There are less than 40 clients. I prefer to minimize the number of servers. Is it possible to use one system for some of this servers:

1. SharePoint

2. Exchange Server

3. SQL Server

4. Active Directory DC

Thank you