Public is related to Tax. Tax is related to Deficit. 
Radiation is a type of Spread. Spread is a synonym of Expand. one thing you do when you Writing is Expand. Desk can be used for Writing. 
Public <--RelatedTo--> Tax <--RelatedTo--> Deficit 
Radiation --IsA--> Spread <--Synonym--> Expand <--HasSubevent-- Writing <--UsedFor-- Desk 