The subnet address ranges for the five areas on your internetwork are:

• Backbone (Area 0): from 172.16.64.0 to 172.16.127.0
• London (Area 1): from 172.16.0.0 to 172.16.31.0
• Dublin (Area 2): from 172.16.192.0 to 172.16.255.0
• Sydney (Area 3): from 172.16.32.0 to 172.16.63.0
• SanFran (Area 4): from 172.16.128.0 to 172.16.191.0

Each area has an area range address mask that defines the range of addresses in that area that are consolidated for route summarization purposes.

For example area 4 consists of 64 subnets from 172.16.128.0 to 172.16.191.0 and each has a subnet mask of 255.255.192.0. Area 3 consists of 32 subnets from 131.108.32.0 to 131.108.63.0 and has a mask of 255.255.224.0.
@@
