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, x_15 will not play tennis. There is at least one x_15 for which x_15 will drink water or x_15 will listen to a song. For all x_15, if x_15 drinks water, then x_15 is playing tennis. For all x_15, x_15 will listen to a song if and only if x_15 will play tennis.
For all x_15, x_15 will not drink water can be inferred via the universal modus tollens rule. For all x_15, if x_15 listens to a song, then x_15 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_15, if x_15 plays tennis, then x_15 is listening to a song can be inferred via the universal biconditional elimination rule. For all x_15, x_15 will not listen to a song can be inferred via the universal biconditional elimination rule.