Translate the following inference to logic notation: For all x, x_3 will climb a mountain. There is at least one x for which x_3 is an electrician if and only if x_3 will play squash. For all x, if x_3 climbs a mountain, then x_3 is playing squash. Therefore there is at least one x for which x_3 is an electrician.
forall x: P(x). exists x: Q(x) <-> R(x). forall x: P(x) -> R(x). Therefore exists x: Q(x).