Show that Zorn’s lemma implies the following:Lemma (Kuratowski). Let  be a collection of s...

Show that Zorn’s lemma implies the following:

Lemma (Kuratowski). Let  be a collection of sets. Suppose that for every subcollection  of  that is simply ordered by proper inclusion, the union of the elements of  belongs to . Then A has an element that is properly contained in no other element of .