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_4, x_4 will make tea or x_4 will take a plane. For all x_4, if x_4 reads a book, then x_4 is playing squash. For all x_4, if x_4 takes a plane, then x_4 is playing squash. For all x_4, if x_4 writes a letter, then x_4 is reading a book. There is at least one x_4 for which x_4 will not make tea or x_4 will write a letter.
For all x_4, if x_4 writes a letter, then x_4 is playing squash can be inferred via the universal transitivity rule. There is at least one x_4 for which x_4 will take a plane or x_4 will write a letter can be inferred via the existential resolution rule.