let $s\,$ be a set with six elements. in how many different ways can one select two not necessarily distinct subsets of $s\,$ so that the union of the two subsets is $s\,$? the order of selection does not matter; for example, the pair of subsets $\{a, c\},\{b, c, d, e, f\}$ represents the same selection as the pair $\{b, c, d, e, f\},\{a, c\}.$