A hub contains a single collision domain and a single broadcast domain, regardless of the number of ports on the hub.
1 broadcast domain and 12 collision domains
Broadcast Domains.
A collision domain consists of all the clients that could possibly cause a collision amongst themselves by sending a packet at the same time. Devices such as hubs create a single collision domain...
Since a router does not forward broadcast messages it automatically splits up the broadcast domains for all clients connected to them.