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: There is at least one x_18 for which x_18 will listen to a song. For all x_18, if x_18 listens to a song, then x_18 is playing tennis. For all x_18, x_18 will make tea. For all x_18, x_18 will play tennis if and only if x_18 will sleep.
There is at least one x_18 for which x_18 will play tennis can be inferred via the existential modus ponens rule. There is at least one x_18 for which x_18 will listen to a song and x_18 will make tea can be inferred via the existential conjunction rule. There is at least one x_18 for which x_18 will make tea and x_18 will listen to a song can be inferred via the existential conjunction rule. For all x_18, if x_18 plays tennis, then x_18 is sleeping can be inferred via the universal biconditional elimination rule. For all x_18, if x_18 sleeps, then x_18 is playing tennis can be inferred via the universal biconditional elimination rule.