Translate the following inference to logic notation: For all x, z_3 is a writer if and only if z_3 is an office clerk. For all x, z_3 is an office clerk. There is at least one x for which z_3 will take a plane. Therefore there is at least one x for which z_3 is a writer and z_3 will take a plane.
forall x: P(x) <-> Q(x). forall x: Q(x). exists x: R(x). Therefore exists x: P(x) and R(x).