New Exchange 2013 Setup (VMware)

Hello all

Appreciate to get help as I’m not very experience in Exchange.

I am planning to install Exchange2013 on VMs.This is a small setup with only 40 mailbox. So I'm going with Exchange2013Enterprise.

For the CAL, if I purchase 40 Enterprise CAL, do I still need to purchase 40 Standard CAL?

I plan to install the Mailbox Server and CAS on separate VM.
I’m using Exchange2013Enterprise for Mailbox Server.
Am I able to use Exchange2013Standard for CAS?

For Exchange2013, is it necessary to place the CAS in the DMZ?

Can the CAS also house the SMTP (in DMZ)?

Or the STMP needs to be both in the LAN and in the DMZ (connector)?

Thanks in advance.

Regards,
Eugene