“All” means no counterexample

Two purchased units are not necessarily two product types. To ask who bought every required product, look for a requirement the customer missed. Accept only when none is missing.

Find a required product with no matching customer purchase. If no such missing product exists, the customer satisfies “all”.

“All” means no counterexample: Find a required product with no matching customer purchase. If no such missing product exists, the customer satisfies “all”.