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 y for which y will not take a plane. For all y, y will take a plane or y is not a taxi driver. For all y, y is a taxi driver if and only if y will take a plane.
For all y, if y were a taxi driver, then y is taking a plane can be inferred via the universal rewriting rule. For all y, if y were a taxi driver, then y is taking a plane can be inferred via the universal biconditional elimination rule. For all y, if y takes a plane, then y is a taxi driver can be inferred via the universal biconditional elimination rule. There is at least one y for which y is not a taxi driver can be inferred via the existential biconditional elimination rule.