Agent is a type of Substance. Agent is related to Air. Air is related to Lung. 
College is related to Establishment. Establishment is related to Shop. you would Shop because Purchase. Purchase is related to Buy. 
Substance <--IsA-- Agent <--RelatedTo--> Air <--RelatedTo--> Lung 
College <--RelatedTo--> Establishment <--RelatedTo--> Shop --MotivatedByGoal--> Purchase <--RelatedTo--> Buy 