Estimate is a synonym of Judge. Judge is related to Legal. Legal is similar to Eligible. Eligible is similar to Suitable. 
Captain is a type of Head. Head is related to Rule. Rule is related to Ability. Availability is derived from Ability. 
Estimate <--Synonym--> Judge <--RelatedTo--> Legal <--SimilarTo--> Eligible <--SimilarTo--> Suitable 
Captain --IsA--> Head <--RelatedTo--> Rule <--RelatedTo--> Ability <--DerivedFrom-- Availability 