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 Barbara were a mechanic, then Michael is happy. If Barbara were a mechanic, then Barbara is curious. Michael is not happy. If Barbara were curious, then Barbara is a mechanic.
Barbara is not a mechanic can be inferred via the modus tollens rule. If Barbara were curious, then Michael is happy can be inferred via the transitivity rule. Barbara is a mechanic if and only if Barbara is curious can be inferred via the biconditional introduction rule. Barbara is curious if and only if Barbara is a mechanic can be inferred via the biconditional introduction rule.