Excel Cruiseline offers nightly dinner cruises departing from several cities on the eastern coast of the United States including Charleston, Baltimore, and Alexandria. Dinner cruise tickets sell for $60 per passenger. Excel Cruiseline's variable cost of providing the dinner is $30 per passenger, and the fixed cost of operating the vessels (depreciation, salaries, docking fees, and other expenses) is $270,000 per month. The company's relevant range extends to 17,000 monthly passengers. The breakeven units are 9,000 tickets sold. If Excel Cruiseline sells 10,000 dinner cruises, compute the margin of safety as a percentage of sales