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 were an electrician, then x_9 is a doctor. For all x_9, if x_9 were a doctor, then x_9 is an electrician. For all x_9, x_9 will drive a car if and only if x_9 is a doctor. For all x_9, x_9 will drive a car or x_9 is an electrician.
For all x_9, x_9 is an electrician if and only if x_9 is a doctor can be inferred via the universal biconditional introduction rule. For all x_9, x_9 is a doctor if and only if x_9 is an electrician can be inferred via the universal biconditional introduction rule. For all x_9, if x_9 drives a car, then x_9 is a doctor can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 were a doctor, then x_9 is driving a car can be inferred via the universal biconditional elimination rule.