License issue about Agent for VMware

Assume that our environment have 3 x Backup Exec 2012 server, 20 x ESX Servers.

I want to assigned for one Backup Exec act as Central Admin Server. Use 3 x Backup Exec server can backup all VMs stored in ESX Servers and use deduplication technology

I know I need the following licenses must be purchase:

3 x Backup Exec 2012 Server License

1 x Enterprise Server Option

3 x Deduplication Option

But I am not sure how many Agent for VMware need to be purchase.

20 x Agent for VMware / Hyper-V for 3 x Backup Exec Servers?

60 x Agent for VMware / Hyper-V for 3 x Backup Exec Servers?

I know Backup Exec Server can share deduplication storage on Central Admin server to other managed Backup Exec Server.  3x Backup Exec server share one deduplication storage can increase deduplication ratio for storage, minimize the use of disk space.

What is the transport mode of backup between Central Admin server and managed Backup Exec Server using deduplication technology? Through network? Can I configure to use SAN for backup data from managed Backup Exec server to Deduplication storage on Central Admin server?

Thanks!