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_1, x_1 will not listen to a song. There is at least one x_1 for which x_1 will make tea if and only if x_1 is a soldier. For all x_1, if x_1 makes tea, then x_1 is listening to a song.
For all x_1, x_1 will not make tea can be inferred via the universal modus tollens rule. There is at least one x_1 for which if x_1 makes tea, then x_1 is a soldier can be inferred via the existential biconditional elimination rule. There is at least one x_1 for which if x_1 were a soldier, then x_1 is making tea can be inferred via the existential biconditional elimination rule.