You are the network administrator for Contoso， Ltd. The network consists of a single Active Directory forest that contains a single domain named contoso.com. You have a user account named CONTOSO\admin that is a member of the Domain Admins global group. You need to create a new child domain named NA.contoso.com in the forest. You install a stand-alone Windows Server 2003 computer named DC3. You use the Active Directory Installation Wizard to promote DC3 to a domain controller in the new domain. You choose to create a domain controller for a new child domain in an existing domain tree. You enter the user name and password for CONTOSO\admin. You choose contoso.com as the parent domain， and you type NA as the name of the child domain. You receive the error message shown in the exhibit. （Click the Exhibit button.） You need to be able to create the new child domain. 
What should you do？（）