Translate the following inference to logic notation: There is at least one x for which z will drink water if and only if z will play squash. For all x, z will drink water if and only if z will read a book. For all x, z will play squash or z will read a book. Therefore there is at least one x for which z will drink water.
exists x: P(x) <-> Q(x). forall x: P(x) <-> R(x). forall x: Q(x) or R(x). Therefore exists x: P(x).