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: Robert is an astronaut if and only if John is playing tennis. If Robert reads a book, then John is playing tennis. For all x_8, x_8 will read a book or x_8 is an astronaut.
If Robert were an astronaut, then John is playing tennis can be inferred via the biconditional elimination rule. If John plays tennis, then Robert is an astronaut can be inferred via the biconditional elimination rule.