What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y_1, if y_1 reads a book, then y_1 is an electrician. For all y_1, if y_1 were an electrician, then y_1 is reading a book. If David were not an electrician, then David is a scientist. David is not reading a book.
For all y_1, y_1 will read a book if and only if y_1 is an electrician. For all y_1, y_1 is an electrician if and only if y_1 will read a book.