Translate the following inference to logic notation: For all x, if x_6 takes a plane, then x_6 is sad. For all x, x_6 is happy or x_6 is a writer. For all x, x_6 is sad or x_6 is not a writer. For all x, x_6 is not happy or x_6 will take a plane. Therefore for all x, x_6 is sad.
forall x: P(x) -> Q(x). forall x: R(x) or S(x). forall x: Q(x) or ~S(x). forall x: ~R(x) or P(x). Therefore forall x: Q(x).