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: William is a janitor if and only if Jessica is making tea. If it rains, then David is an astronaut. If David were an astronaut, then William is a janitor. Jessica is making tea or it is raining.
If it rains, then William is a janitor can be inferred via the transitivity rule. If William were a janitor, then Jessica is making tea can be inferred via the biconditional elimination rule. If Jessica makes tea, then William is a janitor can be inferred via the biconditional elimination rule.