Given the following words {rot, tot, root, toot, roto, toto, too, to, otto}

Let f be the function that maps a word to its bag of letters. For the kernel relation of f, describe the equivalence classes.

I understand the first part of the question but not the second.

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Let R be a relation on a set S such that R is symmetric and transitive and for each x c- S there is an element y c- S ( those are supposed to be the E rounded) such that x R y. Prove that R is an equivalence relation in other words prove that it is reflexive.