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_15, x_15 will sleep if and only if x_15 is a soldier. For all x_15, if x_15 makes tea, then x_15 is a soldier. There is at least one x_15 for which x_15 will make tea or x_15 will sleep. For all x_15, x_15 is not a soldier.
For all x_15, x_15 will not make tea can be inferred via the universal modus tollens rule. For all x_15, if x_15 sleeps, then x_15 is a soldier can be inferred via the universal biconditional elimination rule. For all x_15, if x_15 were a soldier, then x_15 is sleeping can be inferred via the universal biconditional elimination rule. For all x_15, x_15 will not sleep can be inferred via the universal biconditional elimination rule.