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: Jessica is a nurse or Thomas is reading a book. If Thomas reads a book, then Barbara is cooking. Barbara is cooking if and only if Karen is a mechanic. If Jessica were a nurse, then Karen is a mechanic.
If Barbara cooks, then Karen is a mechanic can be inferred via the biconditional elimination rule. If Karen were a mechanic, then Barbara is cooking can be inferred via the biconditional elimination rule.