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 is an artist or x_9 is excited. For all x_9, x_9 is an office clerk or x_9 is not excited. There is at least one x_9 for which x_9 is an office clerk if and only if x_9 is an artist.
For all x_9, if x_9 were excited, then x_9 is an office clerk can be inferred via the universal rewriting rule. There is at least one x_9 for which if x_9 were an office clerk, then x_9 is an artist can be inferred via the existential biconditional elimination rule. There is at least one x_9 for which if x_9 were an artist, then x_9 is an office clerk can be inferred via the existential biconditional elimination rule.