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_12, x_12 will drive a car or x_12 is not a janitor. There is at least one x_12 for which x_12 will not write a letter or x_12 is a writer. For all x_12, x_12 will write a letter or x_12 is a janitor. For all x_12, if x_12 drives a car, then x_12 is a writer. For all x_12, if x_12 were a writer, then x_12 is driving a car.
There is at least one x_12 for which x_12 is a janitor or x_12 is a writer can be inferred via the existential resolution rule. For all x_12, if x_12 were a janitor, then x_12 is driving a car can be inferred via the universal rewriting rule. For all x_12, x_12 will drive a car if and only if x_12 is a writer can be inferred via the universal biconditional introduction rule. For all x_12, x_12 is a writer if and only if x_12 will drive a car can be inferred via the universal biconditional introduction rule.