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: For all z, z is not a sailor. If it is overcast, then Joseph is a mechanic. For all z, z is a sailor or z is not a mechanic.
For all z, if z were a mechanic, then z is a sailor can be inferred via the universal rewriting rule.