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: For all x_9, if x_9 drives a car, then x_9 is playing squash. For all x_9, if x_9 plays squash, then x_9 is driving a car. There is at least one x_9 for which x_9 is not a bartender. For all x_9, if x_9 plays squash, then x_9 is a bartender.
There is at least one x_9 for which x_9 will not play squash can be inferred via the existential modus tollens rule. For all x_9, if x_9 drives a car, then x_9 is a bartender can be inferred via the universal transitivity rule. For all x_9, x_9 will drive a car if and only if x_9 will play squash can be inferred via the universal biconditional introduction rule. For all x_9, x_9 will play squash if and only if x_9 will drive a car can be inferred via the universal biconditional introduction rule.