数列$\left\{a_n\right\}$中，$a_n=2n-106$，则使前n项和$S_n$取得最小值的n的值为 （  ）

便民商店经营一种商品，在销售过程中，发现一周利润y（元）与每件销售价x（元）之间的关系满足y=﹣2（x﹣20）²+1558，由于某种原因，价格只能15≤x≤22，那么一周可获得最大利润是（　　）

A: Hi, Grace.

B: Hi, Tom. ____?

A: My favorite sport is tennis. What about you?

B: I don't like tennis. I like soccer best.

A: ____?

B: Because it's exciting and interesting.

A: Do you play it a lot?

B: ____. I play it three times a week.

A: ____?

B: I play it in my P.E class. We have there P.E. classes a week.

A. That's cool ____.

B: OK.We can meet at my school about 4:00. See you there.