Translate the following inference to logic notation: For all x, z is a writer if and only if z is fast. For all x, z is a writer or z is a mechanic. For all x, z is fast if and only if z is a mechanic. Therefore for all x, z is fast.
forall x: P(x) <-> Q(x). forall x: P(x) or R(x). forall x: Q(x) <-> R(x). Therefore forall x: Q(x).