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 z, if z were a musician, then z is making tea. There is at least one z for which if z makes tea, then z is an office clerk. For all z, z is not an office clerk. For all z, if z were an office clerk, then z is making tea.
There is at least one z for which z will not make tea can be inferred via the existential modus tollens rule. There is at least one z for which if z were a musician, then z is an office clerk can be inferred via the existential transitivity rule. There is at least one z for which z will make tea if and only if z is an office clerk can be inferred via the existential biconditional introduction rule. There is at least one z for which z is an office clerk if and only if z will make tea can be inferred via the existential biconditional introduction rule.