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 will sleep or x_13 will not read a book. For all x_13, x_13 will read a book if and only if x_13 will play tennis. There is at least one x_13 for which if x_13 takes a plane, then x_13 is playing tennis.
For all x_13, if x_13 reads a book, then x_13 is sleeping can be inferred via the universal rewriting rule. For all x_13, if x_13 reads a book, then x_13 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_13, if x_13 plays tennis, then x_13 is reading a book can be inferred via the universal biconditional elimination rule.