Frustration is a type of Emotion. Emotion is related to Poet. Poet is related to Pen. 
Pad is a type of Stuff. Stuff is related to Poet. Poet is related to Emotion. Doubt is a type of Emotion. 
Frustration --IsA--> Emotion <--RelatedTo--> Poet <--RelatedTo--> Pen 
Pad --IsA--> Stuff <--RelatedTo--> Poet <--RelatedTo--> Emotion <--IsA-- Doubt 