Suppose you work for a lab which is studying butterflies. it has a sample of n butterflies, l1, l2, . . , ln. the researchers have made a series of r determinations determining whether two butterflies belong to different species. a determination is of the form (i, j), and it means that li and lj belong to different species. your job is to give an o(n + r) time algorithm to decide whether the determinations are consistent with the butterflies belonging to just two species. (note: it is possible that they could belong to three or more species, but that is a separate question.)