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 drives a car, then Elisabeth is making tea. If Robert were a doctor, then Elisabeth is not making tea. Robert is a doctor if and only if Jennifer is sad. Susan is driving a car.
Elisabeth is making tea can be inferred via the modus ponens rule. If Robert were a doctor, then Jennifer is sad can be inferred via the biconditional elimination rule. If Jennifer were sad, then Robert is a doctor can be inferred via the biconditional elimination rule.