Tough is a synonym of Bad. Bad is the opposite of Proper. Proper is related to Decent. 
House have Bathroom. Bathroom is related to Cabinet. you are likely to find Plastic in/at/on Cabinet. 
Tough <--Synonym--> Bad <--Antonym--> Proper <--RelatedTo--> Decent 
House --HasA--> Bathroom <--RelatedTo--> Cabinet <--AtLocation-- Plastic 