Translate the following inference to logic notation: For all x, z will write a letter if and only if z is an electrician. For all x, if z drinks water, then z is writing a letter. There is at least one x for which z is an artist or z is an electrician. For all x, z is not an artist or z will drink water. Therefore there is at least one x for which z will write a letter.
forall x: P(x) <-> Q(x). forall x: R(x) -> P(x). exists x: S(x) or Q(x). forall x: ~S(x) or R(x). Therefore exists x: P(x).