What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: Mary is sleeping or Joseph is not a sailor. For all z, if z were a sailor, then z is a doctor. For all z, if z were a doctor, then z is a sailor.
If Joseph were a sailor, then Mary is sleeping can be inferred via the rewriting rule. For all z, z is a sailor if and only if z is a doctor can be inferred via the universal biconditional introduction rule. For all z, z is a doctor if and only if z is a sailor can be inferred via the universal biconditional introduction rule.