Luxury 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 $$80$ per passenger. Luxury Cruiseline's variable cost of providing the dinner is $$40$ per passenger, and the fixed cost of operating the vessels $($depreciation$,$ salaries, docking fees, and other expenses$)$ is $$360,000$ per month. The company's relevant range extends to $19,000$ monthly passengers.

Use this information to compute the following:

a$.$ What is the contribution margin per passenger?

b$.$ What is the contribution margin ratio?

c$.$ Use the unit contribution margin to project operating income if monthly sales total $16,000$ passengers.

d$.$ Use the contribution margin ratio to project operating income if monthly sales revenue totals $$775,000.$