Translate the following inference to logic notation: For all x, if x_5 were happy, then x_5 is an electrician. For all x, x_5 is happy if and only if x_5 is a mechanic. There is at least one x for which if x_5 were an electrician, then x_5 is happy. For all x, x_5 is not a mechanic. Therefore there is at least one x for which x_5 is not an electrician.
forall x: P(x) -> Q(x). forall x: P(x) <-> R(x). exists x: Q(x) -> P(x). forall x: ~R(x). Therefore exists x: ~Q(x).