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_4, y_4 is a writer if and only if y_4 is a politician. Richard is a politician or it is overcast. If it is overcast, then Richard is a writer.
For all y_4, if y_4 were a writer, then y_4 is a politician can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were a politician, then y_4 is a writer can be inferred via the universal biconditional elimination rule.