There's basically a lot of otas and especially problems and examples where you have different conditions, different solutions, wrong solutions, or not correct answers. I've been learning 300 pages now, and I think I'm seeing at least 10 errors. And yet, often the publishers have difficulty learning because they provide answers and they don't give them a noon table. I bought it in a university textbook, and I'm not recommending it if I've been purely interested in economic engineering.