题目

Sam Walton, the founder of Wal-Mart, was born in Kingfish, Oklahoma on March 29, 1918. He was raised in Missouri where he worked in his father’s store while attending school. This was his first retailing (零售业) experience and he really enjoyed it. After graduation, he began his own career as a retail merchant. He soon opened his first Wal-Mart store in 1962 in Rogers, Arkansas. Wal-Mart specialized in name brands at low prices and Sam Walton was surprised at the success. Soon a chain of Wal-Mart stores sprang up across rural America. Walton's management style was popular with emplo某校举行“普法”知识竞赛，高二年级共有800名学生参加了这次竞赛．为了解本次竞赛成绩情况，从中抽取了部分学生的成绩进行统计．请你解答下列问题：（1）若用系统抽样的方法抽取50个样本，现将所有学生随机地编号为000，001，002，…，799，若抽样时确定每组都是抽出第5个数，求出第三组抽出的学生的编号；（2）根据（1）中抽取的样本统计得到的频率分布直方图填充频率分布表；（3）若成绩在95分以上的学生设为一等奖，问所有参赛学生中获得一等奖的学生约为多少人？（4）估算出本次竞赛的均分．分组频数频率[60，70]  [70，80]  [80，90]  [90.100]  合计501