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: There is at least one x_14 for which x_14 will sleep or x_14 will take a plane. For all x_14, if x_14 works, then x_14 is sleeping. For all x_14, if x_14 sleeps, then x_14 is working. For all x_14, x_14 will not work.
For all x_14, x_14 will not sleep can be inferred via the universal modus tollens rule. For all x_14, x_14 will work if and only if x_14 will sleep can be inferred via the universal biconditional introduction rule. For all x_14, x_14 will sleep if and only if x_14 will work can be inferred via the universal biconditional introduction rule.