Translate the following inference to logic notation: For all x, x_14 is a lawyer or x_14 is not sad. For all x, x_14 is an artist or x_14 is not a lawyer. For all x, x_14 is sad or x_14 is not an artist. Therefore for all x, x_14 is sad if and only if x_14 is an artist.
forall x: P(x) or ~Q(x). forall x: R(x) or ~P(x). forall x: Q(x) or ~R(x). Therefore forall x: Q(x) <-> R(x).