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: Elisabeth is a janitor or Barbara is drinking water. Elisabeth is a janitor if and only if it is sunny. It is raining and Robert is playing squash. It is not sunny.
It is raining can be inferred via the simplification rule. Robert is playing squash can be inferred via the simplification rule. If Elisabeth were a janitor, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then Elisabeth is a janitor can be inferred via the biconditional elimination rule. Elisabeth is not a janitor can be inferred via the biconditional elimination rule.