You have an Exchange Server 2010 organization. The organization has 500 mailboxes and three servers. The
servers are configured as shown in the following table.
EX10EDGE is located in the perimeter network. EX10CH has an Edge Subscription. All Internet mail flows
through EX10EDGE.
You deploy an Exchange Server 2016 Mailbox server named EX16MBX to the organization. You deploy an
Exchange Server 2016 Edge Transport server named EX16EDGEtothe perimeter network.
You need to transition all Internet mail to flow through EX16EDGE. The solution must minimize disruptions to
the mail flow.
Which three actions should you perform in sequence? To answer, move the appropriate actions from the list of
actions to the answer area and arrange them in the correct order.
Select and Place:
Answer: 
Given answer is correct
Yes, I agree:
https://technet.microsoft.com/en-us/library/bb331973(v=exchg.160).aspx
That seems correct:
1) Create an Edge Subscription between EX16EDGE and EX16MBX
This will allow the traffic from the MBX servers to the outside world and back
2) Configure the perimeter firewall to forward SMTP traffic to EX16EDGE
This will reroute the traffic through the new EDGE but won’t interrupt the existing subscriptions (meeting the requirements – minimize disruptions)
3) Remove the Edge Subscription on EX10CH and EX10EDGE
This will make the mails flow through other exchange servers and through the new EDGE server