On a 30-question test, Question 1 is worth 1 point, Question 2 is worth 2 points, and so on up to Question 30. David takes the test and afterward finds out he answered nine of the questions incorrectly. However, he was not told which nine were incorrect. What is the highest possible score he could have attained?

Let's think step by step and output the final answer within \boxed{}.
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