What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Jessica is not taking a plane. Joseph is a sailor if and only if Sarah is playing squash. Joseph is a sailor if and only if Jessica is a writer. If Jessica were a writer, then Jessica is taking a plane. If Sarah plays squash, then Joseph is a sailor.
Jessica is not a writer. If Joseph were a sailor, then Sarah is playing squash. If Joseph were a sailor, then Jessica is a writer. If Sarah plays squash, then Joseph is a sailor. If Jessica were a writer, then Joseph is a sailor.