Difficulty is related to Level. Level is a type of Place. Place is a synonym of Invest. Invest is a type of Install. 
Cool is related to Interest. Interest is related to Amount. Amount is related to Weight. Load is a type of Weight. 
Difficulty <--RelatedTo--> Level --IsA--> Place <--Synonym--> Invest --IsA--> Install 
Cool <--RelatedTo--> Interest <--RelatedTo--> Amount <--RelatedTo--> Weight <--IsA-- Load 