2015年10月14日，国家统计局发布数据显示，9月份，全国工业生产者出厂价格指数PPI同比下滑4.8%，从长远来看，PPI连续下滑对生产带来的影响（   ）。

①企业营利能力减弱  ②工业产品价格下降  ③经济下行压力较大

④促进社会经济发展  ⑤企业生产规模缩小  ⑥居民购买力增强

In 1638, John Harvard donated some money and about four hundred books to a new university. This was the beginning of the library at Harvard University. The gift was so important that the university was named for John Harvard.
Thomas Bray began the first free lending library in the late 1600s. He set up more than 30 or these libraries in the American colonies. However, the idea for this kind of free library ended when Bray died in 1730. In 1731, Benjamin Franklin and some friends started the first subscription（订阅费） library in the United States. In a subscription library people pay money to become members, but they may borrow the books without paying again.
In the United States, every child had a free education. This idea soon led to free libraries. One of the first libraries that used tax money to buy books was a library in Peterborough, New Hampshire. This library was set up in 1833.

如图，MN是⊙O的直径，若∠A=10°，∠PMQ=40°，以PM为边作圆的内接正多边形，则这个正多边形是____ 边形．