Translate the following inference to logic notation: For all x, if x_11 were an electrician, then x_11 is not playing squash. For all x, x_11 is a musician if and only if x_11 is an electrician. Charles is a musician if and only if Mary is sad. For all x, x_11 will play squash. Therefore Mary is not sad.
forall x: P(x) -> ~Q(x). forall x: R(x) <-> P(x). R(a) <-> p. forall x: Q(x). Therefore ~p.