根据短文理解，选择正确答案。

    There are fifty students in our class. There are twenty-four boys and twenty-six girls. Some students live near the school, and some others live far from school. About half of the students usually come to school by bike. They often get to school at a quarter to seven. About fifteen students often come to school by bus. They often get to school very early, too. Another ten students come to school on foot. Their homes are near the school, but they are often late for school, because they get up late.

（Ⅰ）求出表中N及a，b，c的值；

（Ⅱ）求频率分布直方图中d的值；

（Ⅲ）从该产品中随机抽取一件，试估计这件产品的质量少于25千克的概率．

5个男生站一排，每2个男生中间站 3个女生，女生比男生多几人?