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: It is raining if and only if Richard is sleeping. If Sarah works, then Richard is sleeping. It is not raining.
If it rains, then Richard is sleeping can be inferred via the biconditional elimination rule. If Richard sleeps, then it is raining can be inferred via the biconditional elimination rule. Richard is not sleeping can be inferred via the biconditional elimination rule.