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, if x were fast, then x is not listening to a song. For all x, if x were fast, then x is reading a book. For all x, x will listen to a song. There is at least one x for which if x reads a book, then x is fast.
For all x, x is not fast can be inferred via the universal modus tollens rule. There is at least one x for which x will read a book if and only if x is fast can be inferred via the existential biconditional introduction rule. There is at least one x for which x is fast if and only if x will read a book can be inferred via the existential biconditional introduction rule.