<span>As many times as necessary.
An essay may need to be revised until the author of it is satisfied. </span>
The caged bird represents Angelou's<span> confinement resulting from racism and oppression.</span>
I think the single sentence that shows it is a personal letter is "that all I can say is that I am well" as the rest of the letter is details about his military campaign so could be part of a more formal memo if it were not for this opening sentence so that seems to be how to identify it as such.
