Translate the following inference to logic notation: For all x, x_6 will play squash if and only if x_6 will write a letter. For all x, x_6 is poor. There is at least one x for which x_6 will climb a mountain if and only if x_6 will write a letter. For all x, if x_6 plays squash, then x_6 is not poor. Therefore there is at least one x for which x_6 will not climb a mountain.
forall x: P(x) <-> Q(x). forall x: R(x). exists x: S(x) <-> Q(x). forall x: P(x) -> ~R(x). Therefore exists x: ~S(x).