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_5 for which x_5 is a writer if and only if x_5 is a taxi driver. For all x_5, if x_5 were a writer, then x_5 is a taxi driver.
There is at least one x_5 for which if x_5 were a writer, then x_5 is a taxi driver can be inferred via the existential biconditional elimination rule. There is at least one x_5 for which if x_5 were a taxi driver, then x_5 is a writer can be inferred via the existential biconditional elimination rule.