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: Barbara is not a bartender. Sarah is cooking if and only if Linda is writing a letter. Barbara is a bartender if and only if Sarah is cooking. For all x_15, if x_15 goes running, then x_15 is writing a letter.
If Sarah cooks, then Linda is writing a letter can be inferred via the biconditional elimination rule. If Barbara were a bartender, then Sarah is cooking can be inferred via the biconditional elimination rule. If Linda writes a letter, then Sarah is cooking can be inferred via the biconditional elimination rule. If Sarah cooks, then Barbara is a bartender can be inferred via the biconditional elimination rule. Sarah is not cooking can be inferred via the biconditional elimination rule.