Great 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 $ 50 per passenger. Great Cruiseline's variable cost of providing the dinner is $ 20 per passenger, and the fixed cost of operating the vessels (depreciation, salaries, docking fees, and other expenses) is $ 210 comma 000 per month. The company's relevant range extends to 18 comma 000 monthly passengers. If Great Cruiseline sells an additional 600 tickets, by what amount will its operating income increase (or operating loss decrease)?