What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y_3, if y_3 were fast, then y_3 is a nurse. For all y_3, if y_3 were a nurse, then y_3 is fast. There is at least one y_3 for which if y_3 were a nurse, then y_3 is fast.
For all y_3, y_3 is fast if and only if y_3 is a nurse. For all y_3, y_3 is a nurse if and only if y_3 is fast. There is at least one y_3 for which y_3 is a nurse if and only if y_3 is fast. There is at least one y_3 for which y_3 is fast if and only if y_3 is a nurse.