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 Joseph were a musician, then Barbara is sad. Barbara is sad if and only if Joseph is a musician. Barbara is not sad.
Joseph is not a musician can be inferred via the modus tollens rule. If Barbara were sad, then Joseph is a musician can be inferred via the biconditional elimination rule. If Joseph were a musician, then Barbara is sad can be inferred via the biconditional elimination rule. Joseph is not a musician can be inferred via the biconditional elimination rule.