Overtaken vessel has the right of way and priority. The overtaking vessel has the responsibility. Procedure is to contact them on VHF or if they don't answer use the horn with one or two blasts depending on your intention (passing to port or to starboard). If they don't answer signifying agreement it's ALL on you. Check the inland rules side of the page as there are often other diffences such as in curves or upstream/downstream situations.

Unfortunately they aren't violating Rule 5 either.

Cheers

Michael S :)