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 snowing if and only if Charles is climbing a mountain. For all z, z is not poor. If it snows, then Joseph is poor.
If it snows, then Charles is climbing a mountain can be inferred via the biconditional elimination rule. If Charles climbs a mountain, then it is snowing can be inferred via the biconditional elimination rule.