Translate the following inference to logic notation: For all x, x_7 is a poet if and only if x_7 will drink water. There is at least one x for which x_7 will write a letter. For all x, if x_7 writes a letter, then x_7 is drinking water. Therefore there is at least one x for which x_7 is a poet.
forall x: P(x) <-> Q(x). exists x: R(x). forall x: R(x) -> Q(x). Therefore exists x: P(x).