Line is related to Flat. Flat is related to Leaf. Leaf is related to Single. Single is a synonym of Individual. 
Estimated is the opposite of Actual. Actual is the opposite of Future. Future is the opposite of Historical. Historical is a synonym of Old. 
Line <--RelatedTo--> Flat <--RelatedTo--> Leaf <--RelatedTo--> Single <--Synonym--> Individual 
Estimated <--Antonym--> Actual <--Antonym--> Future <--Antonym--> Historical <--Synonym--> Old 