A data center network engineer is designing OSPF areas for a Nexus 9000 fabric. Area 20 contains only leaf switches that need to reach external networks redistributed into OSPF by an ASBR in another area, but the engineer wants to suppress the individual external (Type 5) LSAs to reduce the link-state database size on the leaves while still allowing inter-area summary (Type 3) routes and injecting a default route for external destinations. Which OSPF area type should be configured for Area 20?