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 z_1, if z_1 drives a car, then z_1 is sleeping. There is at least one z_1 for which z_1 is an office clerk if and only if z_1 will drive a car. For all z_1, if z_1 sleeps, then z_1 is driving a car.
For all z_1, z_1 will drive a car if and only if z_1 will sleep can be inferred via the universal biconditional introduction rule. For all z_1, z_1 will sleep if and only if z_1 will drive a car can be inferred via the universal biconditional introduction rule. There is at least one z_1 for which if z_1 were an office clerk, then z_1 is driving a car can be inferred via the existential biconditional elimination rule. There is at least one z_1 for which if z_1 drives a car, then z_1 is an office clerk can be inferred via the existential biconditional elimination rule.