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_18, x_18 is bored or x_18 will make tea. For all x_18, if x_18 were a soldier, then x_18 is listening to a song. For all x_18, x_18 is not a cashier or x_18 is a soldier. For all x_18, if x_18 were bored, then x_18 is a cashier. There is at least one x_18 for which if x_18 makes tea, then x_18 is a cashier. For all x_18, x_18 is a nurse if and only if x_18 will listen to a song.
There is at least one x_18 for which x_18 is a cashier can be inferred via the existential disjunction elimination rule. For all x_18, if x_18 were a nurse, then x_18 is listening to a song can be inferred via the universal biconditional elimination rule. For all x_18, if x_18 listens to a song, then x_18 is a nurse can be inferred via the universal biconditional elimination rule.