You need to create a Federation Trust for the planned organization relationship.
Which three actions should you perform?
Answer: 
Explanation:
1.Run the Get-ExchangeCertificatecmdlet
2.Run the Get-FederatedDomainProofcmdlet
3.Create a Text (TXT) Record
Reference: http://johanveldhuis.nl/?p=2418&lang=en
Note:
This example retrieves the Self-Signed Certificate and creates the Federation Trust “Microsoft Federation
Gateway”.
This automatically deploys the Self-Signed Certificate to the Exchange Servers in your Organization.
Get-ExchangeCertificate | ?{$_.friendlyname -eq “Exchange Federated Sharing”} | NewFederationTrust -Name “Microsoft Federation Gateway” *Configure Federated Sharing
Step 1:
Create and configure a Federation Trust Use the New-FederationTrust cmdlet to set up a federation trust
between your Exchange organization and the Microsoft Federation Gateway.
Step 2:
Create an organization relationship
Step 3:
Create a sharing policy This example creates the sharing policy Contoso for the external Federated Domain
contoso.com.
This Policy allows users in the contoso.com domain to see your user’s detailed calendar availability (free/busy)
information and contacts.
By default, this policy is enabled.
New-SharingPolicy -Name “Contoso” -Domains contoso.com: CalendarSharingFreeBusyDetail,
ContactsSharing
Step 4:
Configure an Autodiscover Public DNS Record You need to add an alias Canonical Name (CNAME) Resource
Record to your Public-Facing DNS.
The new CNAMERecord should point to an Internet-facing Exchange2013 Client Access Server that’s running
the Autodiscover Service.