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 will drink water or y is not rich. There is at least one y for which y is rich if and only if y is a cashier.
For all y, if y were rich, then y is drinking water can be inferred via the universal rewriting rule. There is at least one y for which if y were rich, then y is a cashier can be inferred via the existential biconditional elimination rule. There is at least one y for which if y were a cashier, then y is rich can be inferred via the existential biconditional elimination rule.