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, x_9 will take a plane if and only if x_9 will drive a car. For all x_9, x_9 will not drive a car. There is at least one x_9 for which x_9 is poor if and only if x_9 will take a plane.
For all x_9, if x_9 takes a plane, then x_9 is driving a car can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which if x_9 were poor, then x_9 is taking a plane can be inferred via the existential biconditional elimination rule. For all x_9, if x_9 drives a car, then x_9 is taking a plane can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which if x_9 takes a plane, then x_9 is poor can be inferred via the existential biconditional elimination rule. For all x_9, x_9 will not take a plane can be inferred via the universal biconditional elimination rule.