Translate the following inference to logic notation: If Sarah were fast, then Thomas is running. If Thomas goes running, then Sarah is fast. William is not writing a letter. If Thomas goes running, then William is taking a plane. For all x, if z takes a plane, then z is writing a letter. Therefore Sarah is not fast.
p -> q. q -> p. ~P(a). q -> Q(a). forall x: Q(x) -> P(x). Therefore ~p.