Translate the following inference to logic notation: For all x, x will take a plane if and only if x is a doctor. For all x, x will take a plane if and only if x is a doctor. Therefore for all x, x is a doctor if and only if x will take a plane.
forall x: P(x) <-> Q(x). forall x: P(x) <-> Q(x). Therefore forall x: Q(x) <-> P(x).