The legibility of a text depends, among other things, on the length of the sentences. Short sentences read more easily than long sentences. If you assume that just about every new sentence starts with a capital letter, and that there are not too many uppercase abbreviations, then the ratio of the number of capital letters to the total number of letters is a good measure of the length of the sentences. It is now up to you to make a good estimate of the proportion of capitals for a working text (which consists of approximately 40 pages and 70,000 letters). How are you going to do that? Do you use an EAS? What should you do then? Do you use a staged sample? How would you do that? Are there different options?