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: If John writes a letter, then Robert is running. Michael is not sleeping. Michael is sleeping or Richard is playing squash. It is not windy. Robert is running if and only if it is windy.
Richard is playing squash can be inferred via the disjunctive syllogism rule. Michael is not sleeping and it is not windy can be inferred via the conjunction rule. It is not windy and Michael is not sleeping can be inferred via the conjunction rule. If Robert goes running, then it is windy can be inferred via the biconditional elimination rule. If it is windy, then Robert is running can be inferred via the biconditional elimination rule. Robert is not running can be inferred via the biconditional elimination rule.