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 it is cold, then Barbara is a mechanic. Barbara is a mechanic or Richard is not bored. If Barbara were a mechanic, then it is cold.
If Richard were bored, then Barbara is a mechanic can be inferred via the rewriting rule. It is cold if and only if Barbara is a mechanic can be inferred via the biconditional introduction rule. Barbara is a mechanic if and only if it is cold can be inferred via the biconditional introduction rule.