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_15, if x_15 climbs a mountain, then x_15 is listening to a song. James is not listening to a song. For all z, if z takes a plane, then z is fast. James is climbing a mountain if and only if Joseph is fast.
If James climbs a mountain, then Joseph is fast can be inferred via the biconditional elimination rule. If Joseph were fast, then James is climbing a mountain can be inferred via the biconditional elimination rule.