Solution is a type of Method. Solution is related to Reply. Reply is related to Action. 
Cluster is a type of Meet. Meet is a synonym of Fit. Fit is related to Narrow. Narrow is a synonym of Specialize. 
Method <--IsA-- Solution <--RelatedTo--> Reply <--RelatedTo--> Action 
Cluster --IsA--> Meet <--Synonym--> Fit <--RelatedTo--> Narrow <--Synonym--> Specialize 