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: It is late or Elisabeth is not taking a plane. It is late if and only if it is raining.
If Elisabeth takes a plane, then it is late can be inferred via the rewriting rule. If it is late, then it is raining can be inferred via the biconditional elimination rule. If it rains, then it is late can be inferred via the biconditional elimination rule.