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 write a letter. William is reading a book if and only if it is windy. If William writes a letter, then it is windy.
If William reads a book, then it is windy can be inferred via the biconditional elimination rule. If it is windy, then William is reading a book can be inferred via the biconditional elimination rule.