Translate the following inference to logic notation: For all x, x_9 will not work. For all x, x_9 is an electrician if and only if x_9 will work. There is at least one x for which if x_9 writes a letter, then x_9 is an electrician. For all x, if x_9 takes a plane, then x_9 is writing a letter. Therefore there is at least one x for which x_9 will not take a plane.
forall x: ~P(x). forall x: Q(x) <-> P(x). exists x: R(x) -> Q(x). forall x: S(x) -> R(x). Therefore exists x: ~S(x).