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_5, x_5 is a writer if and only if x_5 will play squash. For all x_5, x_5 will not play squash. For all x_5, if x_5 were a writer, then x_5 is playing squash.
For all x_5, x_5 is not a writer can be inferred via the universal modus tollens rule. For all x_5, if x_5 were a writer, then x_5 is playing squash can be inferred via the universal biconditional elimination rule. For all x_5, if x_5 plays squash, then x_5 is a writer can be inferred via the universal biconditional elimination rule. For all x_5, x_5 is not a writer can be inferred via the universal biconditional elimination rule.