每张奖券中尾奖的概率为<imgwidth="21"height="41"v:shapes="_x0000_i1093"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image126.png">,某人购买了20张号码杂乱的奖券,则中尾奖的张数<imgwidth="19"height="17"v:shapes="_x0000_i1094"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb08.files/image002.png">服从()分布。