Translate the following inference to logic notation: If David were a server, then Barbara is a janitor. If David were not a server, then it is late. For all x, x_17 is a scientist if and only if x_17 is a janitor. For all x, x_17 is not a scientist. Therefore it is late.
p -> P(a). ~p -> q. forall x: Q(x) <-> P(x). forall x: ~Q(x). Therefore q.