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 is not happy. For all x_4, if x_4 were a doctor, then x_4 is fast. For all x_4, x_4 is happy if and only if x_4 is fast. For all x_4, if x_4 reads a book, then x_4 is a doctor.
For all x_4, if x_4 reads a book, then x_4 is fast can be inferred via the universal transitivity rule. For all x_4, if x_4 were happy, then x_4 is fast can be inferred via the universal biconditional elimination rule. For all x_4, if x_4 were fast, then x_4 is happy can be inferred via the universal biconditional elimination rule. For all x_4, x_4 is not fast can be inferred via the universal biconditional elimination rule.