MB4 236b: Does Eating or Sleeping Location Determine Obligation Towards an Eruv (370:4-5)

If many people eat in one dining room but sleep in their own apartment, do they need an eruv? What if the group wants to make an eruv with another group?

The dwelling in which the eruv is placed doesn't need to contribute to the eruv.

If people are sleeping in one place but eating in another place, with whom do they make an eruv - where they eat or where they sleep?