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 z for which if z plays squash, then z is reading a book. For all z, if z reads a book, then z is playing squash. For all z, z will play squash or z will not read a book.
For all z, if z reads a book, then z is playing squash can be inferred via the universal rewriting rule. There is at least one z for which z will play squash if and only if z will read a book can be inferred via the existential biconditional introduction rule. There is at least one z for which z will read a book if and only if z will play squash can be inferred via the existential biconditional introduction rule.