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_4, x_4 will not read a book. For all x_4, x_4 is a sailor or x_4 will not read a book. There is at least one x_4 for which if x_4 were a sailor, then x_4 is reading a book.
There is at least one x_4 for which x_4 is not a sailor can be inferred via the existential modus tollens rule. For all x_4, if x_4 reads a book, then x_4 is a sailor can be inferred via the universal rewriting rule.