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 y_4, y_4 will not read a book. There is at least one y_4 for which if y_4 reads a book, then y_4 is a mechanic. For all y_4, y_4 will read a book if and only if y_4 is a mechanic.
For all y_4, if y_4 reads a book, then y_4 is a mechanic can be inferred via the universal biconditional elimination rule. For all y_4, if y_4 were a mechanic, then y_4 is reading a book can be inferred via the universal biconditional elimination rule. For all y_4, y_4 is not a mechanic can be inferred via the universal biconditional elimination rule.