Let X = {−1, 0, 1} and A = (x)
and define a relation R on A as follows:
For all sets s and t in
(x), s R t ⇔
the sum of the elements in s equals the sum of the elements in t.
It is a fact that R is an equivalence relation on A. Use set-roster notation to list the distinct equivalence classes of R. (Enter your answer as a comma-separated list of sets. Enter EMPTY or ∅ for the empty set.)