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 is excited. For all x_13, x_13 is excited if and only if x_13 is poor. For all x_13, if x_13 makes tea, then x_13 is poor. For all x_13, if x_13 were a janitor, then x_13 is making tea. For all x_13, if x_13 were poor, then x_13 is playing squash.
For all x_13, if x_13 makes tea, then x_13 is playing squash can be inferred via the universal transitivity rule. For all x_13, if x_13 were a janitor, then x_13 is poor can be inferred via the universal transitivity rule. For all x_13, if x_13 were excited, then x_13 is poor can be inferred via the universal biconditional elimination rule. For all x_13, if x_13 were poor, then x_13 is excited can be inferred via the universal biconditional elimination rule.