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_9 for which x_9 is a musician if and only if x_9 is an electrician. For all x_9, x_9 will cook if and only if x_9 is a musician. For all x_9, if x_9 were an electrician, then x_9 is reading a book. For all x_9, x_9 will not read a book.
For all x_9, x_9 is not an electrician can be inferred via the universal modus tollens rule. For all x_9, if x_9 cooks, then x_9 is a musician can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which if x_9 were a musician, then x_9 is an electrician can be inferred via the existential biconditional elimination rule. For all x_9, if x_9 were a musician, then x_9 is cooking can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which if x_9 were an electrician, then x_9 is a musician can be inferred via the existential biconditional elimination rule.