You need to prevent the domain controller from registering Host (A) records for the 10.10.10.5 IP address
You need to ensure that the computers in nwtraders.com can update their Host (A) records on any of the DNS servers in the forest
You need to ensure that the stale resource records are automatically removed from the contoso.com zone
You need to ensure that the host (A) records for the removed computers are automatically deleted from the contoso.com DNS zone