Nixon and Co$.,$ CPAs, issued an unmodified or unqualified opinion on the $2015$ financial statements of Madison Corp. These financial statements were included in Madison$$s annual report and Form $10-$K filed with the SEC. Nixon did not detect material misstatements in the financial statements as a result of negligence in the performance of the audit. Based upon the financial statements, Harry purchased stock in Madison. Shortly thereafter, Madison became insolvent, causing the price of the stock to decline drastically. Harry has commenced legal action against Nixon for damages based upon Section $10($b$)$ and Rule $10$b$-5$ of the Securities Exchange Act of $1934.$ What would be Nixon$$s best defense to such an action? Explain.