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_6, if x_6 were a janitor, then x_6 is poor. There is at least one x_6 for which x_6 will read a book if and only if x_6 will write a letter. For all x_6, if x_6 were poor, then x_6 is writing a letter.
For all x_6, if x_6 were a janitor, then x_6 is writing a letter can be inferred via the universal transitivity rule. There is at least one x_6 for which if x_6 reads a book, then x_6 is writing a letter can be inferred via the existential biconditional elimination rule. There is at least one x_6 for which if x_6 writes a letter, then x_6 is reading a book can be inferred via the existential biconditional elimination rule.