Translate the following inference to logic notation: Mary is not an electrician. For all x, if z_1 writes a letter, then z_1 is an electrician. For all x, if z_1 writes a letter, then z_1 is an electrician. For all x, if z_1 were an electrician, then z_1 is writing a letter. Therefore Mary is not writing a letter.
~P(a). forall x: Q(x) -> P(x). forall x: Q(x) -> P(x). forall x: P(x) -> Q(x). Therefore ~Q(a).