Translate the following inference to logic notation: There is at least one x for which x_15 is a taxi driver if and only if x_15 will sleep. For all x, if x_15 were a taxi driver, then x_15 is not a writer. For all x, x_15 is a writer. For all x, if x_15 sleeps, then x_15 is taking a plane. For all x, x_15 will sleep or x_15 will not take a plane. Therefore there is at least one x for which x_15 will not take a plane.
exists x: P(x) <-> Q(x). forall x: P(x) -> ~R(x). forall x: R(x). forall x: Q(x) -> S(x). forall x: Q(x) or ~S(x). Therefore exists x: ~S(x).