145, No. 21 Senate Proceedings, Day Sixteen, February 6, 1999, Senate, sitting as a Court of Impeachment, continued consideration of the articles of impeachment against William Jefferson Clinton, President of the United States, receiving the presentation of evidence from the House managers and White House counsel.
However, a possible answer is 2 or more, that is the number of LAN interfaces that appears as outgoing interfaces/next-hops. The serial interface is a separate broadcast domain / IP subnet but it is point to point link. Nothing can be said about the remote IP subnets we can guess that IP subnet 192.168.90.0/24 belongs to a LAN interface of another router. This can be counted as the third broadcast domain.
In a subnet, usually the broadcast IP address is the last IP address. As example, the broadcast IP address of 192.168.0.0/29 subnet is the 192.168.0.7/29. In broadcast network, there is also a term called Network ID. Network ID is an IP address that is used to identify specific subnet.