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: John is not making tea. If Sarah sleeps, then John is rich. If Barbara plays squash, then Sarah is sleeping. For all y_1, y_1 will make tea if and only if y_1 is rich.
If Barbara plays squash, then John is rich can be inferred via the transitivity rule. For all y_1, if y_1 makes tea, then y_1 is rich can be inferred via the universal biconditional elimination rule. For all y_1, if y_1 were rich, then y_1 is making tea can be inferred via the universal biconditional elimination rule.