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: There is at least one x_5 for which if x_5 were a janitor, then x_5 is a writer. For all x_5, if x_5 were a janitor, then x_5 is making tea. For all x_5, if x_5 makes tea, then x_5 is a janitor.
There is at least one x_5 for which if x_5 makes tea, then x_5 is a writer can be inferred via the existential transitivity rule. For all x_5, x_5 is a janitor if and only if x_5 will make tea can be inferred via the universal biconditional introduction rule. For all x_5, x_5 will make tea if and only if x_5 is a janitor can be inferred via the universal biconditional introduction rule.