Translate the following inference to logic notation: There is at least one x for which y_3 will drink water and y_3 will sleep. For all x, y_3 will drink water if and only if y_3 is a nurse. Therefore there is at least one x for which y_3 is a nurse.
exists x: P(x) and Q(x). forall x: P(x) <-> R(x). Therefore exists x: R(x).