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_13, x_13 will not sleep. For all x_13, x_13 will sleep if and only if x_13 will write a letter. For all x_13, if x_13 sleeps, then x_13 is writing a letter. For all x_13, x_13 will write a letter or x_13 will drive a car.
For all x_13, if x_13 sleeps, then x_13 is writing a letter can be inferred via the universal biconditional elimination rule. For all x_13, if x_13 writes a letter, then x_13 is sleeping can be inferred via the universal biconditional elimination rule. For all x_13, x_13 will not write a letter can be inferred via the universal biconditional elimination rule.