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_3, if x_3 works, then x_3 is writing a letter. For all x_3, x_3 is not bored or x_3 will work. There is at least one x_3 for which if x_3 sleeps, then x_3 is writing a letter. For all x_3, x_3 is bored.
Nothing can be inferred from these premises.