Great Cruiseline offers nightly dinner cruises departing from several cities on the East 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 $210,000 per month. The company's relevant range extends to 20,000 monthly passengers. If Great Cruiseline has a target operating income of $45,000 per month, how many dinner cruise tickets must the company sell? First, identify the formula, then compute the targot sales in units