SK: We now have on the order of 2,200 videos, covering everything from basic arithmetic, all the way to vector calculus, and some of the stuff that you saw up there.
SK:我们现在有共计 2200个视频， 它们涵盖了从基础算术 到矢量微积分的全部内容。 而且在你刚刚看到的一些视频中，