Translate the following inference to logic notation: For all x, if x_15 were a sailor, then x_15 is playing squash. Elisabeth is taking a plane if and only if John is sad. If John were sad, then Linda is a sailor. Therefore if Elisabeth takes a plane, then Linda is playing squash.
forall x: P(x) -> Q(x). p <-> q. q -> P(a). Therefore p -> Q(a).