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_13, x_13 is a writer if and only if x_13 will work. There is at least one x_13 for which x_13 is not poor. For all x_13, if x_13 works, then x_13 is not a politician. For all x_13, x_13 is poor or x_13 is a politician.
There is at least one x_13 for which x_13 is a politician can be inferred via the existential disjunctive syllogism rule. For all x_13, if x_13 were a writer, then x_13 is working can be inferred via the universal biconditional elimination rule. For all x_13, if x_13 works, then x_13 is a writer can be inferred via the universal biconditional elimination rule.