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_8, x_8 will take a plane or x_8 will listen to a song. For all x_8, x_8 will not play a game. There is at least one x_8 for which x_8 is happy. For all x_8, x_8 will take a plane if and only if x_8 will play a game.
For all x_8, if x_8 takes a plane, then x_8 is playing a game can be inferred via the universal biconditional elimination rule. For all x_8, if x_8 plays a game, then x_8 is taking a plane can be inferred via the universal biconditional elimination rule. For all x_8, x_8 will not take a plane can be inferred via the universal biconditional elimination rule.