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: There is at least one x_10 for which if x_10 were excited, then x_10 is an office clerk. For all x_10, if x_10 were an office clerk, then x_10 is excited. For all x_10, x_10 is not an office clerk. For all x_10, x_10 is excited or x_10 will read a book.
There is at least one x_10 for which x_10 is not excited can be inferred via the existential modus tollens rule. There is at least one x_10 for which x_10 is excited if and only if x_10 is an office clerk can be inferred via the existential biconditional introduction rule. There is at least one x_10 for which x_10 is an office clerk if and only if x_10 is excited can be inferred via the existential biconditional introduction rule.