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_7, if x_7 reads a book, then x_7 is sleeping. For all x_7, x_7 is a doctor or x_7 will read a book. For all x_7, x_7 is not a doctor or x_7 will play tennis. There is at least one x_7 for which x_7 will sleep if and only if x_7 will play tennis.
For all x_7, x_7 will read a book or x_7 will play tennis can be inferred via the universal resolution rule. There is at least one x_7 for which if x_7 sleeps, then x_7 is playing tennis can be inferred via the existential biconditional elimination rule. There is at least one x_7 for which if x_7 plays tennis, then x_7 is sleeping can be inferred via the existential biconditional elimination rule.