The essay overall is ok however there are some things that you can do to make it better.

Both the introduction and conclusion are too short, try mentioning more about: context, audience, structure, tone, and authorial intent in the introduction.

In your first two body paragraphs, I feel you need a bit more clarity, to help you show the assessor that you really understand how Summers builds his argument. They are also a little bit short and could use an extra sentence or two.

"Freedom is a value that most Americans enjoy" Do not make blatant assumptions about the audience, instead write something like: Through this technique, Summers appeals to his audience's sense of freedom etc.

The last body paragraph is really good if you feel more comfortable with writing about evidence I advise that you write this paragraph first. Some statements you used like: "This strategy is effective and provides a concrete base for his other persuasive techniques" would really set up the essay as a whole of you put it in your first body paragraph.

Just remember that you are trying to show the assessor how much you understand about how the author structures his/her argument to persuade the audience. Always keep coming back to this idea throughout your essay no matter if you're writing about, evidence, reasoning, or the use of metalanguage.

Also if you have time before the test write an essay by hand.