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_10, x_10 is not a writer. For all x_10, x_10 is not a politician or x_10 will drive a car. For all x_10, x_10 is a politician or x_10 is happy. For all x_10, x_10 is happy if and only if x_10 is a writer. There is at least one x_10 for which x_10 is a janitor.
For all x_10, x_10 is happy or x_10 will drive a car can be inferred via the universal resolution rule. For all x_10, if x_10 were happy, then x_10 is a writer can be inferred via the universal biconditional elimination rule. For all x_10, if x_10 were a writer, then x_10 is happy can be inferred via the universal biconditional elimination rule. For all x_10, x_10 is not happy can be inferred via the universal biconditional elimination rule.