Law is related to Brief. Brief is related to Statement. Statement is related to Account. Charge is a type of Account. 
Quantity is related to Magnitude. Magnitude is related to Size. Size is related to Drop. 
Law <--RelatedTo--> Brief <--RelatedTo--> Statement <--RelatedTo--> Account <--IsA-- Charge 
Quantity <--RelatedTo--> Magnitude <--RelatedTo--> Size <--RelatedTo--> Drop 