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 fast or y is not a nurse. There is at least one y for which if y were fast, then y is a nurse. For all y, if y were a nurse, then y is fast.
For all y, if y were a nurse, then y is fast can be inferred via the universal rewriting rule. There is at least one y for which y is fast if and only if y is a nurse can be inferred via the existential biconditional introduction rule. There is at least one y for which y is a nurse if and only if y is fast can be inferred via the existential biconditional introduction rule.