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_7, if x_7 listens to a song, then x_7 is playing squash. For all x_7, if x_7 plays squash, then x_7 is climbing a mountain. For all x_7, x_7 will climb a mountain if and only if x_7 will work.
For all x_7, if x_7 listens to a song, then x_7 is climbing a mountain can be inferred via the universal transitivity rule. For all x_7, if x_7 climbs a mountain, then x_7 is working can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 works, then x_7 is climbing a mountain can be inferred via the universal biconditional elimination rule.