A word is considered elfish if it contains the letters: e, l, and f in it, in any order. For example, we would say that the following words are elfish: whiteleaf, tasteful, unfriendly, and waffles, because they each contain those letters. Write a predicate function in c++ called elfish? that, given a word, tells us if that word is elfish or not. The function should take as input a string (and at least one other parameter) and return a Boolean value.