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 Linda were sad, then Sarah is a taxi driver. If Linda were poor, then Sarah is a taxi driver. For all x_17, x_17 is poor or x_17 is sad. Susan is taking a plane if and only if Sarah is a taxi driver.
If Susan takes a plane, then Sarah is a taxi driver can be inferred via the biconditional elimination rule. If Sarah were a taxi driver, then Susan is taking a plane can be inferred via the biconditional elimination rule.