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: There is at least one x_9 for which x_9 will drive a car or x_9 will work. For all x_9, if x_9 drives a car, then x_9 is sad. For all x_9, if x_9 were rich, then x_9 is sad. For all x_9, if x_9 works, then x_9 is rich. For all x_9, if x_9 were sad, then x_9 is rich.
For all x_9, if x_9 drives a car, then x_9 is rich can be inferred via the universal transitivity rule. For all x_9, if x_9 works, then x_9 is sad can be inferred via the universal transitivity rule. For all x_9, x_9 is rich if and only if x_9 is sad can be inferred via the universal biconditional introduction rule. For all x_9, x_9 is sad if and only if x_9 is rich can be inferred via the universal biconditional introduction rule.