Translate the following inference to logic notation: There is at least one x for which if x_6 were happy, then x_6 is a writer. For all x, if x_6 were a lawyer, then x_6 is happy. For all x, if x_6 were a writer, then x_6 is a taxi driver. For all x, if x_6 were a taxi driver, then x_6 is a lawyer. Therefore there is at least one x for which x_6 is a writer if and only if x_6 is a lawyer.
exists x: P(x) -> Q(x). forall x: R(x) -> P(x). forall x: Q(x) -> S(x). forall x: S(x) -> R(x). Therefore exists x: Q(x) <-> R(x).