Translate the following inference to logic notation: David is taking a plane if and only if Karen is a soldier. David is not taking a plane. Karen is a sailor or Karen is not a soldier. For all x, if x_4 were a sailor, then x_4 is a soldier. Therefore Karen is not a sailor.
p <-> P(a). ~p. Q(a) or ~P(a). forall x: Q(x) -> P(x). Therefore ~Q(a).