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_16, x_16 is sad. For all x_16, if x_16 were a nurse, then x_16 is happy. There is at least one x_16 for which if x_16 were happy, then x_16 is not running. For all x_16, x_16 will go running if and only if x_16 is sad.
For all x_16, if x_16 goes running, then x_16 is sad can be inferred via the universal biconditional elimination rule. For all x_16, if x_16 were sad, then x_16 is running can be inferred via the universal biconditional elimination rule.