(a) A food service worker is any employee who is primarily engaged in the serving of food or beverages to guests, patrons or customers in the hospitality industry, including, but not limited to, wait staff, bartenders, captains and bussing personnel; and who regularly receives tips from such guests, patrons or customers. The term food service worker shall not include delivery workers.

(b) Classification as a food service worker shall be on a weekly basis except that an employee may not be classified as a food service worker on any day in such week in which she or he has been assigned to work in an occupation in which tips are not customarily received for two hours or more or for more than 20 percent of her or his shift, whichever is less.