Transportation is related to Street. you are likely to find Policeman in/at/on Street. Inspector is a type of Policeman. 
Volume is related to Low. Low is related to Sale. Sale is related to Cheap. 
Transportation <--RelatedTo--> Street <--AtLocation-- Policeman <--IsA-- Inspector 
Volume <--RelatedTo--> Low <--RelatedTo--> Sale <--RelatedTo--> Cheap 