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_13, x_13 will drink water if and only if x_13 is rich. For all x_13, if x_13 were an office clerk, then x_13 is rich. For all x_13, if x_13 drinks water, then x_13 is working. For all x_13, x_13 will not work. For all x_13, if x_13 works, then x_13 is drinking water.
For all x_13, x_13 will not drink water can be inferred via the universal modus tollens rule. For all x_13, x_13 will drink water if and only if x_13 will work can be inferred via the universal biconditional introduction rule. For all x_13, x_13 will work if and only if x_13 will drink water can be inferred via the universal biconditional introduction rule. For all x_13, if x_13 drinks water, then x_13 is rich can be inferred via the universal biconditional elimination rule. For all x_13, if x_13 were rich, then x_13 is drinking water can be inferred via the universal biconditional elimination rule.