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_5, if x_5 were a taxi driver, then x_5 is sad. There is at least one x_5 for which x_5 is sad if and only if x_5 will go running. For all x_5, x_5 will go running or x_5 is a taxi driver.
There is at least one x_5 for which if x_5 were sad, then x_5 is running can be inferred via the existential biconditional elimination rule. There is at least one x_5 for which if x_5 goes running, then x_5 is sad can be inferred via the existential biconditional elimination rule.