I think that each may book should at least have all problem solutions at least, and most problem resolutions as well, leaving some room problem to be solved wit

I think that each may book should at least have all problem solutions at least, and most problem resolutions as well, leaving some room problem to be solved without giving the resolution, for training. Anything short of that can only be used as a reference book by a teacher, because teachers need to confirm that the resolution is indeed complete and right. Without that, as a engineering and economics student (decades ago), my resolutions would often have been incomplete and lack some details and specific cases.