A service provider runs OSPFv3 for IPv6 in their core. An ABR connects Area 0 to Area 20, which contains only stub routers with no need to reach redistributed external destinations directly, but those routers DO need summary routes for inter-area prefixes to reach the rest of the network. The design team wants to minimize the LSA database in Area 20 by blocking Type 5 external LSAs while still permitting inter-area (Type 3) LSAs. Which area configuration on the ABR meets this requirement?