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 x_7 for which x_7 is a taxi driver or x_7 is an astronaut. For all x_7, x_7 is a taxi driver if and only if x_7 will go running. For all x_7, if x_7 plays tennis, then x_7 is running. For all x_7, if x_7 were an astronaut, then x_7 is playing tennis.
For all x_7, if x_7 were an astronaut, then x_7 is running can be inferred via the universal transitivity rule. For all x_7, if x_7 were a taxi driver, then x_7 is running can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 goes running, then x_7 is a taxi driver can be inferred via the universal biconditional elimination rule.