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 x_6, x_6 is fast. There is at least one x_6 for which if x_6 were a nurse, then x_6 is drinking water. For all x_6, if x_6 were a nurse, then x_6 is not fast. For all x_6, if x_6 drinks water, then x_6 is a nurse.
For all x_6, x_6 is not a nurse can be inferred via the universal modus tollens rule. There is at least one x_6 for which x_6 is a nurse if and only if x_6 will drink water can be inferred via the existential biconditional introduction rule. There is at least one x_6 for which x_6 will drink water if and only if x_6 is a nurse can be inferred via the existential biconditional introduction rule.