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 x_3, x_3 will go running if and only if x_3 will take a plane. There is at least one x_3 for which x_3 will go running.
For all x_3, if x_3 goes running, then x_3 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_3, if x_3 takes a plane, then x_3 is running can be inferred via the universal biconditional elimination rule.