某商场“五.一”期间举行有奖促销活动,顾客只要在商店购物满800元就能得到一次摸奖机会.摸奖规则是:在盒子内预先放有5个相同的球,其中一个球标号是0,两个球标号都是40,还有两个球没有标号.顾客依次从盒子里摸球,每次摸一个球(不放回),若累计摸到两个没有标号的球就停止摸球,否则将盒子内球摸完才停止.奖金数为摸出球的标号之和(单位:元),已知某顾客得到一次摸奖机会.
(Ⅰ)求该顾客摸三次球被停止的概率;
(Ⅱ)设ξ(元)为该顾客摸球停止时所得的奖金数,求ξ的分布列及数学期望Eξ.
考点分析:
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