Refer to the exhibit.

An enterprise has three sites over a Layer 2 Metro Ethernet ELAN service. 100Mb/s and 10 Mb/s links have been provisioned to provide redundancy for the head office. When OSPF routing enabled to provide connectivity and the correct bandwidth statement has been applied to each interface, the branch sites observe two equal-cost routes to the head office. The enterprise wants to send all traffic through the 100 Mb/s link and use the 10Mb/S link strictly as a backup. Which OSPF network type must be set to ensure that the head office 100 Mb/s circuit is preferred over the 10 Mb/s circuit, at the same time minimize the amount of configuration required on all of the routers throughout the network?