Translate the following inference to logic notation: For all x, y is a politician or y is not a taxi driver. There is at least one x for which y is a taxi driver if and only if y is a politician. Therefore there is at least one x for which y is a taxi driver if and only if y is a politician.
forall x: P(x) or ~Q(x). exists x: Q(x) <-> P(x). Therefore exists x: Q(x) <-> P(x).