Translate the following inference to logic notation: There is at least one x for which z_3 is an artist if and only if z_3 is a musician. For all x, if z_3 were an artist, then z_3 is writing a letter. For all x, if z_3 writes a letter, then z_3 is an artist. For all x, z_3 is not a musician. Therefore there is at least one x for which z_3 will not write a letter.
exists x: P(x) <-> Q(x). forall x: P(x) -> R(x). forall x: R(x) -> P(x). forall x: ~Q(x). Therefore exists x: ~R(x).