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_5, x_5 is a nurse if and only if x_5 will drink water. For all x_5, if x_5 were a nurse, then x_5 is drinking water. There is at least one x_5 for which x_5 will not drink water.
There is at least one x_5 for which x_5 is not a nurse can be inferred via the existential modus tollens rule. For all x_5, if x_5 were a nurse, then x_5 is drinking water can be inferred via the universal biconditional elimination rule. For all x_5, if x_5 drinks water, then x_5 is a nurse can be inferred via the universal biconditional elimination rule. There is at least one x_5 for which x_5 is not a nurse can be inferred via the existential biconditional elimination rule.