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, y will write a letter if and only if y will read a book. If it is sunny, then Susan is writing a letter. For all y, y will not read a book.
For all y, if y writes a letter, then y is reading a book can be inferred via the universal biconditional elimination rule. For all y, if y reads a book, then y is writing a letter can be inferred via the universal biconditional elimination rule. For all y, y will not write a letter can be inferred via the universal biconditional elimination rule.