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, z is not an office clerk. For all z, z is an office clerk if and only if z is a lawyer. For all z, z is a lawyer or z is a taxi driver.
For all z, if z were an office clerk, then z is a lawyer can be inferred via the universal biconditional elimination rule. For all z, if z were a lawyer, then z is an office clerk can be inferred via the universal biconditional elimination rule. For all z, z is not a lawyer can be inferred via the universal biconditional elimination rule.