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_12 for which if x_12 were rich, then x_12 is a doctor. For all x_12, x_12 is a doctor if and only if x_12 will take a plane. For all x_12, x_12 will drive a car or x_12 is rich. For all x_12, x_12 will drive a car if and only if x_12 will take a plane.
For all x_12, if x_12 were a doctor, then x_12 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 drives a car, then x_12 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 takes a plane, then x_12 is a doctor can be inferred via the universal biconditional elimination rule. For all x_12, if x_12 takes a plane, then x_12 is driving a car can be inferred via the universal biconditional elimination rule.