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, x will drink water or x is not sad. For all x, x will read a book if and only if x will drink water. For all x, x will not read a book.
For all x, if x were sad, then x is drinking water can be inferred via the universal rewriting rule. For all x, if x reads a book, then x is drinking water can be inferred via the universal biconditional elimination rule. For all x, if x drinks water, then x is reading a book can be inferred via the universal biconditional elimination rule. For all x, x will not drink water can be inferred via the universal biconditional elimination rule.