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 bartender or x_13 will not work. For all x_13, if x_13 were fast, then x_13 is a bartender. For all x_13, if x_13 were a writer, then x_13 is working. For all x_13, if x_13 were a bartender, then x_13 is fast.
For all x_13, if x_13 works, then x_13 is a bartender can be inferred via the universal rewriting rule. For all x_13, x_13 is fast if and only if x_13 is a bartender can be inferred via the universal biconditional introduction rule. For all x_13, x_13 is a bartender if and only if x_13 is fast can be inferred via the universal biconditional introduction rule.