What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Robert is not reading a book. James is writing a letter if and only if Barbara is drinking water. Barbara is drinking water if and only if Robert is reading a book.
If James writes a letter, then Barbara is drinking water. If Barbara drinks water, then Robert is reading a book. If Barbara drinks water, then James is writing a letter. If Robert reads a book, then Barbara is drinking water. Barbara is not drinking water.