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 were sad, then y_1 is reading a book. There is at least one y_1 for which if y_1 reads a book, then y_1 is sad.
There is at least one y_1 for which y_1 will read a book if and only if y_1 is sad. There is at least one y_1 for which y_1 is sad if and only if y_1 will read a book.