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 John were a scientist, then James is a poet. If James were a poet, then John is a scientist. If David were a taxi driver, then John is a scientist. If John were a scientist, then David is a taxi driver. David is not a taxi driver.
John is not a scientist can be inferred via the modus tollens rule. If James were a poet, then David is a taxi driver can be inferred via the transitivity rule. If David were a taxi driver, then James is a poet can be inferred via the transitivity rule. John is a scientist if and only if James is a poet can be inferred via the biconditional introduction rule. James is a poet if and only if John is a scientist can be inferred via the biconditional introduction rule. David is a taxi driver if and only if John is a scientist can be inferred via the biconditional introduction rule. John is a scientist if and only if David is a taxi driver can be inferred via the biconditional introduction rule.