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_7, x_7 is a writer if and only if x_7 is a carpenter. For all x_8, x_8 is a carpenter.
For all x_7, if x_7 were a writer, then x_7 is a carpenter can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were a carpenter, then x_7 is a writer can be inferred via the universal biconditional elimination rule.