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: William is running if and only if Elisabeth is taking a plane. If William goes running, then David is a carpenter. Elisabeth is taking a plane.
If William goes running, then Elisabeth is taking a plane can be inferred via the biconditional elimination rule. If Elisabeth takes a plane, then William is running can be inferred via the biconditional elimination rule.