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 y, if y were a lawyer, then y is driving a car. For all y, if y drives a car, then y is a taxi driver. For all y, if y were a taxi driver, then y is a lawyer. There is at least one y for which if y were a taxi driver, then y is driving a car.
For all y, if y were a lawyer, then y is a taxi driver can be inferred via the universal transitivity rule. For all y, if y drives a car, then y is a lawyer can be inferred via the universal transitivity rule. For all y, if y were a taxi driver, then y is driving a car can be inferred via the universal transitivity rule. There is at least one y for which y is a taxi driver if and only if y will drive a car can be inferred via the existential biconditional introduction rule. There is at least one y for which y will drive a car if and only if y is a taxi driver can be inferred via the existential biconditional introduction rule.