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: If David goes running, then Charles is climbing a mountain. Charles is climbing a mountain if and only if David is running.
If Charles climbs a mountain, then David is running can be inferred via the biconditional elimination rule. If David goes running, then Charles is climbing a mountain can be inferred via the biconditional elimination rule.