Filtering an array of managed objects by another array of managed objects

I have a mutable array of managed objects that I get from Core Data - let's call them ObjectA. ObjectA has a many-to-many relationship with ObjectB, such that each ObjectA has an NSSet of ObjectBs. ObjectB has a one-to-many relationship with ObjectC, i.e. each ObjectB has one ObjectC. I have a mutable array of managed objects that