Mary is a waitress (女服务生)．She works at a busy restaurant She lakes people's orders(订单) and serves (供应)them food．She also takes people's money and gives them change(零钱)．When the restaurant is really busy．sometimes she even cooks tire food．She works six days a week．Her job is not easy．The trays(盘子) of food are heavy．She always gels backaches from carrying the heavy trays．Besides that．she has to be on her feet(站着)all day．Often her feet get tired．Mary doesn't mainly like her job．but she has to work because she needs the money．She hopes she can find a better job soon.
What dopes Mary do at tile restaurant?