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: For all z, z is not a janitor. Charles is cooking if and only if Barbara is sad. Joseph is a soldier if and only if Joseph is a janitor. Charles is not cooking.
If Charles cooks, then Barbara is sad can be inferred via the biconditional elimination rule. If Joseph were a soldier, then Joseph is a janitor can be inferred via the biconditional elimination rule. If Barbara were sad, then Charles is cooking can be inferred via the biconditional elimination rule. If Joseph were a janitor, then Joseph is a soldier can be inferred via the biconditional elimination rule. Barbara is not sad can be inferred via the biconditional elimination rule.