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_4, x_4 is not rich. For all x_4, if x_4 were a nurse, then x_4 is reading a book. For all x_4, x_4 is rich if and only if x_4 will drink water. For all x_4, if x_4 reads a book, then x_4 is drinking water.
For all x_4, if x_4 were a nurse, then x_4 is drinking water can be inferred via the universal transitivity rule. For all x_4, if x_4 were rich, then x_4 is drinking water can be inferred via the universal biconditional elimination rule. For all x_4, if x_4 drinks water, then x_4 is rich can be inferred via the universal biconditional elimination rule. For all x_4, x_4 will not drink water can be inferred via the universal biconditional elimination rule.