题干

有一个公用电话亭,里面有一部电话,在观察使用这部电话的人的流量时,设在某一时刻,有n个人正在使用电话或等待使用的概率为P(n),且P(n)与时刻t无关,统计得到P(n)= {(
1
2
)
n
·P(0)1n6
0,n7
,那么在某一时刻,这个公用电话亭里一个人也没有的概率P(0)的值是____
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                                                             The advantages of Eating Fruits & Vegetables
      Vegetables and fruit are good for your health because of a lot of vitamins, nutrients(矿物质) and fiber(纤维)in them. Fruits and vegetables are regarded as a healthy diet without adding chemicals or additives(添加剂) for carrying or storing foods. The United States Department of Agriculture suggests eating plenty of fruits and vegetables every day to get the advantages of eating a healthy diet.
Disease Prevention
       The United States Department of Agriculture tells that eating fruits and vegetables helps fight strokes, cardiovascular disease and type 2 diabetes. Because of the potassium in fruits and vegetables, they can prevent the risk of developing kidney stones. The fiber in fruits and vegetables helps the body fight against coronary heart disease.
Idea Health
      Since fruits and vegetables add to a balanced and healthy diet, eating these will help you with your idea. The vitamins in fruits and vegetables helps fight depress(沮丧), according to the Mental Health Foundation. Vitamin B and folic acid found in some vegetables and bananas help you to relax. Eating fruits and vegetables can also help improve memory.
Healthy Weight
      Eating fruits and vegetables helps you have a healthy weight. Fruits and vegetables naturally include less energy than other foods, according to the Center for Disease Control and Prevention. The fiber and water in the fruits and vegetables make you feel that you are full, so you will not feel that you have to eat more food.