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_9, x_9 will drink water or x_9 will listen to a song. For all x_9, if x_9 were a doctor, then x_9 is a carpenter. For all x_9, x_9 will not drink water. There is at least one x_9 for which x_9 is a carpenter if and only if x_9 will listen to a song.
For all x_9, x_9 will listen to a song can be inferred via the universal disjunctive syllogism rule. There is at least one x_9 for which if x_9 were a carpenter, then x_9 is listening to a song can be inferred via the existential biconditional elimination rule. There is at least one x_9 for which if x_9 listens to a song, then x_9 is a carpenter can be inferred via the existential biconditional elimination rule.