Write structures for the diastereomers of 2,3-diphenyl-2-butene and assign each diastereomer its (E) or (Z) designation. Hydrogenation of one of these diastereomers using a palladium catalyst produces a racemic form; similar treatment of the other produces a meso compound. On the basis of these experiments, tell which diastereomer is (E) and which is (Z).