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, if x_4 writes a letter, then x_4 is a lawyer. For all x_4, x_4 is a writer. For all x_4, x_4 will write a letter.
For all x_4, x_4 is a lawyer can be inferred via the universal modus ponens rule. For all x_4, x_4 is a writer and x_4 will write a letter can be inferred via the universal conjunction rule. For all x_4, x_4 will write a letter and x_4 is a writer can be inferred via the universal conjunction rule.