Translate the following inference to logic notation: Thomas is an artist if and only if Barbara is a poet. For all x, x_7 is a janitor if and only if x_7 is an artist. For all x, x_2 is not a poet. Therefore Thomas is not a janitor.
P(a) <-> Q(b). forall x: R(x) <-> P(x). forall x: ~Q(x). Therefore ~R(a).