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 David makes tea, then Mary is cooking. If Mary cooks, then David is making tea. Richard is not a musician. Richard is a musician if and only if Mary is cooking.
David is making tea if and only if Mary is cooking can be inferred via the biconditional introduction rule. Mary is cooking if and only if David is making tea can be inferred via the biconditional introduction rule. If Richard were a musician, then Mary is cooking can be inferred via the biconditional elimination rule. If Mary cooks, then Richard is a musician can be inferred via the biconditional elimination rule. Mary is not cooking can be inferred via the biconditional elimination rule.