There is a hierarchy of importance in the words and phrases quoted in the last posting. The meanings of "carrying on" and "trade or business" are more important than the meaning of "ordinary and necessary" because they have broader impact. As writers and artisans doing freelancing and worried about taxation and minimizing taxes, it is important to know the hierarchy. Next time we will talk about what it means to carry on.
So for now, at ease and carry on. Sayonara.