Hello, I have a problem that I am struggling to get my head around recreating within FME. The images below are just for example.

I have data from two separate sources for which I want to calculate the area of overlap, for each instance parcel data and problem area data.

I want to calculate the area of overlap for every individual parcel and every individual problem area. 

So rather than calculating the overlap for every individual parcel against the entire other layer as would be the case in the image below:
 

I want to calculate the overlap for EACH SINGLE feature, and essentially create a list, so I can then also see the attributes for the problem area, and the area of overlap that particular parcels has with that particular problem area, to then go on and filter out those that fall under a certain threshold of overlap.
 

I have gotten up to the stage of generating a list, which has the parcel id’s and problem id’s for each instance of overlap. My issue is where to go from here and then calculate the overlap for each instance, as exampled in the above image.

 

I believe I need to do some form of FeatureJoining and Group By processing to achieve this, but if anyone knows the most processing efficient way to do this it would be greatly appreciated, as I will need to replicate this process many times over.