Consumer is related to Product. Product is related to Oil. Plastic is created by Oil. 
Sing is a type of Interpret. Sing is a different concept from Double. Double is related to Pair. Couple is a type of Pair. 
Consumer <--RelatedTo--> Product <--RelatedTo--> Oil <--CreatedBy-- Plastic 
Interpret <--IsA-- Sing <--DistinctFrom--> Double <--RelatedTo--> Pair <--IsA-- Couple 