算式：____

C

    The government in China plans to end its one-child policy (政策) and let families have two children instead. The plan was meant to balance (平衡) population development and stop a falling birth rate (出生率).

    China started the one-child policy in the 1980s. But the government allowed only a small number of couples to have two children. For example, some families in the countryside could have two children, if the first-born child is a girl. In 2013, the Chinese government gave other couples a chance to have two children if one of them was an only child.

    Jiang Quanbao, a population expert, explained how Chinese families react to the newest policy. "Lots of young people in the cities are no longer interested in having a second child," he said.

    At the end of 2014, China had a population of 1.37 billion people. But the labor market population will drop in 35 years. That is to say, the country will be in great need of labor by the year 2050. With the "two children" policy, an increase in births can solve this problem.

下列关于物种灭绝的叙述中，正确的是(　　)

从某小区抽取100户居民进行月用电量调查，发现其用电量都在50至350度之间，频率分布直方图如图所示：

（Ⅰ）直方图中x的值为____；

（Ⅱ）在这些用户中，用电量落在区间100，250）内的户数为____．