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_12, if x_12 plays squash, then x_12 is not making tea. For all x_12, if x_12 writes a letter, then x_12 is playing squash. For all x_12, if x_12 reads a book, then x_12 is writing a letter. There is at least one x_12 for which x_12 will make tea.
There is at least one x_12 for which x_12 will not play squash can be inferred via the existential modus tollens rule. For all x_12, if x_12 reads a book, then x_12 is playing squash can be inferred via the universal transitivity rule.