RBR50 use as a sattelite

I know this has been asked but I cannot find the answer. 

I have a RBR50 system with two satilites.  I recently moved and needed to hook up to Xfinity via a cable modem so I purchased the CBR40-100NAS.  It works great with the two original  satilites.  Now I have the old but still good RBR50 home base that I don’t know what to do with.  I do have a separate, one room “casita” at my new home that needs a satilites (wi-fi /Internet).

Can I use the RBR50 base as a satilites with the new cable modem?  OR, is there another alternative to use the old base station to get wi-fi (internet) to my separate room which is only 10 feet from my main house?

Thank you.