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 Susan were a taxi driver, then Joseph is sad. William is not a sailor. Susan is a taxi driver. William is a sailor if and only if James is a bartender.
Joseph is sad can be inferred via the modus ponens rule. William is not a sailor and Susan is a taxi driver can be inferred via the conjunction rule. Susan is a taxi driver and William is not a sailor can be inferred via the conjunction rule. If William were a sailor, then James is a bartender can be inferred via the biconditional elimination rule. If James were a bartender, then William is a sailor can be inferred via the biconditional elimination rule. James is not a bartender can be inferred via the biconditional elimination rule.