IUPAC name for Dibenzalacetone: The molecule is symmetric with 2 benzene rings on each end and a ketone in the center.

So is the "longest chain" that is to give the root of the name considered to be one of the 6C benzenes.

OR is the root of the name considered to be the 5C central chain which contains the ketone as a substituent??

If one of the benzenes is used as the base name, then is the other simply added to the name of substituent?