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 z for which z will not make tea. For all z, if z makes tea, then z is a taxi driver. For all z, z is a taxi driver if and only if z will make tea.
For all z, if z were a taxi driver, then z is making tea can be inferred via the universal biconditional elimination rule. For all z, if z makes tea, then z is a taxi driver can be inferred via the universal biconditional elimination rule. There is at least one z for which z is not a taxi driver can be inferred via the existential biconditional elimination rule.