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_15 for which x_15 is poor if and only if x_15 will drive a car. For all x_15, if x_15 takes a plane, then x_15 is poor. For all x_15, x_15 is an office clerk or x_15 will not drive a car. For all x_15, if x_15 were an office clerk, then x_15 is taking a plane.
For all x_15, if x_15 were an office clerk, then x_15 is poor can be inferred via the universal transitivity rule. For all x_15, if x_15 drives a car, then x_15 is an office clerk can be inferred via the universal rewriting rule. There is at least one x_15 for which if x_15 were poor, then x_15 is driving a car can be inferred via the existential biconditional elimination rule. There is at least one x_15 for which if x_15 drives a car, then x_15 is poor can be inferred via the existential biconditional elimination rule.