Help with licensing

Hi,

We use backup Exec 2012 to backup the following;

1. Windows Server 2003 32-bit domaincontroller, Backup Exec 2012 trial is installed here.

2. Windows Server 2003 32-bit print server, it's also got a SQL database

3. Windows Server 2003 32-bit mail server, Exchange 2003 runs here.

I gather we need to purchase the following

1x Backup Exec 2012 (installed on domaincontroller)

1x Agent for Windows (for backing up the domaincontroller).

2x Agent for Applications and databases (for backing up Exchange (GRT) and SQL on printserver)

Is this correct? Is it true we need to purchase an Agent for Windows for the server where backup exec is installed? Do we need more Agents for Windows?

Thanks in advance,

Justin