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 y, y is not a nurse. For all y, if y were a soldier, then y is a nurse. For all y, y is a nurse if and only if y is a soldier.
For all y, y is not a soldier can be inferred via the universal modus tollens rule. For all y, if y were a nurse, then y is a soldier can be inferred via the universal biconditional elimination rule. For all y, if y were a soldier, then y is a nurse can be inferred via the universal biconditional elimination rule. For all y, y is not a soldier can be inferred via the universal biconditional elimination rule.