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: Elisabeth is not a lawyer. If Thomas were sad, then Michael is a scientist. For all z_2, z_2 is not a scientist. If Elisabeth were a lawyer, then Thomas is reading a book. If Thomas reads a book, then Elisabeth is a lawyer.
Thomas is not reading a book can be inferred via the modus tollens rule. Elisabeth is a lawyer if and only if Thomas is reading a book can be inferred via the biconditional introduction rule. Thomas is reading a book if and only if Elisabeth is a lawyer can be inferred via the biconditional introduction rule.